Knowt
Biology 21st Century (OCR)
Chapter B1: You and your genes
1. Chromosomes, Genes, and DNA
Chromosomes: These are thread-like structures found in the nucleus of cells. They are made of DNA and protein. Think of them as packages that contain genetic information.
DNA (Deoxyribonucleic Acid): This is the molecule that carries genetic information. DNA has a double helix structure, like a twisted ladder. The rungs of the ladder are made of chemical bases (Adenine, Thymine, Guanine, Cytosine - often shortened to A, T, G, C). The sequence of these bases is the genetic code.
Genes: Genes are segments of DNA that contain the instructions for building specific proteins. Proteins control most processes in the body, determining traits like eye color, hair color, and even some aspects of behavior. Imagine genes as specific recipes within the DNA cookbook.
Analogy: Think of a library (nucleus) that contains many books (chromosomes). Each book contains many recipes (genes), and the recipes are written in an alphabet (DNA bases).
2. Heredity and Variation
Living things produce offspring of the same kind: Cats have kittens, dogs have puppies, and humans have babies. Offspring generally resemble their parents.
Offspring vary and are not identical to their parents: While offspring are of the "same kind," they are not exact copies of their parents (except in asexual reproduction). There's variation. For example, kittens from the same litter can have slightly different fur colors or patterns. Siblings share similarities but are also unique.
Heredity: This is the process by which genetic information is passed from parents to offspring. It's why offspring resemble their parents. Genes are the units of heredity, transmitted from one generation to the next.
Genetic information transmission: Parents pass on their genes to their offspring through reproduction. This ensures continuity of species but also introduces variation.
Importance of Variation: Variation is crucial for the survival of species. It allows populations to adapt to changing environments. Some variations might be more advantageous than others in a particular environment (this is the basis of natural selection and evolution, concepts usually explored in later Key Stages).
3. Location of Genetic Information
Genetic information is stored in the nucleus: The nucleus is the control center of the cell. In eukaryotic cells (cells with a nucleus, like animal and plant cells), the chromosomes, and therefore DNA and genes, are located within the nucleus.
Why the nucleus? The nucleus protects the DNA. DNA is vital for the cell's function and the organism's traits, so it's kept safe within a membrane-bound organelle.
4. Contributions to the DNA Model
Watson, Crick, Wilkins, and Franklin: These are key scientists who played crucial roles in discovering the structure of DNA.
James Watson and Francis Crick: They are most famous for building the first accurate model of DNA's double helix structure in 1953. They used data from other scientists to piece together their model.
Rosalind Franklin: Her X-ray diffraction images of DNA were crucial evidence for the double helix shape. Image "Photo 51" was particularly important, providing Watson and Crick with critical measurements and insights.
Maurice Wilkins: He also used X-ray diffraction to study DNA and shared his data with Watson and Crick, which helped them in their modeling.
Importance of their work: Understanding DNA's structure was a massive breakthrough in biology. It paved the way for understanding how DNA replicates, how genes work, and how genetic information is encoded and passed on.
5. Sexual Reproduction in Animals
Sexual Reproduction: Involves two parents and the fusion of gametes (sex cells) to produce offspring.
Gametes: These are specialized sex cells.
Sperm cells (male gametes) and egg cells (female gametes) in animals.
Gametes are haploid, meaning they contain half the number of chromosomes compared to normal body cells.
Fertilization: This is the process where a sperm cell and an egg cell fuse together.
During fertilization, the nuclei of the two gametes join, combining their chromosomes.
The result is a zygote, which is the first cell of a new organism. The zygote is diploid, meaning it has the full set of chromosomes (half from each parent).
Development: The zygote divides and develops into an embryo, and eventually a new individual.
Genetic Variation in Sexual Reproduction: Because offspring inherit half their genes from each parent, sexual reproduction leads to genetic variation in the offspring. This is different from asexual reproduction where offspring are genetically identical to the parent.
6. Sexual and Asexual Reproduction in Plants
Sexual Reproduction in Plants: Many plants reproduce sexually using flowers.
Flower Structures: Flowers are the reproductive organs of plants. Key parts include:
Petals: Often colorful to attract pollinators.
Sepals: Usually green, protect the flower bud.
Stamen: Male part, consists of anther (produces pollen) and filament (stalk).
Pistil/Carpel: Female part, consists of stigma (receives pollen), style (tube), and ovary (contains ovules/eggs).
Pollination: Transfer of pollen from the anther to the stigma.
Pollination methods: Wind, insects, birds, other animals.
Fertilization in Plants:
After pollination, a pollen tube grows from the pollen grain down the style to the ovary.
Sperm cells from the pollen travel down the pollen tube to fertilize the egg cell(s) in the ovule(s).
Fertilization results in a zygote, which develops into an embryo within a seed. The ovary develops into a fruit, which aids in seed dispersal.
Asexual Reproduction in Plants: Some plants can reproduce asexually, creating genetically identical offspring.
Methods of Asexual Reproduction:
Runners: Stems that grow horizontally above ground (e.g., strawberries).
Rhizomes: Stems that grow horizontally underground (e.g., ginger, ferns).
Bulbs: Underground buds (e.g., onions, daffodils).
Tubers: Underground stems with buds (e.g., potatoes).
Cuttings: Pieces of stems or leaves that can grow into new plants.
Tissue culture: Growing plants from small pieces of tissue in a lab.
Advantages of Asexual Reproduction: Rapid reproduction, only one parent needed, offspring are well-suited to a stable environment (if the parent is).
Disadvantages of Asexual Reproduction: Lack of genetic variation, all offspring are susceptible to the same diseases or environmental changes.
Chapter B2: Keeping healthy
1. Healthy Human Diet
Components of a Healthy Diet: A balanced diet includes all the nutrients your body needs to function properly. These are:
Carbohydrates: Main source of energy for the body. Found in foods like bread, rice, pasta, potatoes, and fruits. They are broken down into glucose to provide energy.
Lipids (Fats and Oils): Provide energy, help insulate the body, and are needed for cell function. Found in foods like butter, oils, nuts, and fatty fish. There are different types of fats (saturated and unsaturated), and it's important to have a balance.
Proteins: Essential for growth, repair, and building tissues like muscles, skin, and hair. Found in foods like meat, fish, eggs, beans, lentils, and nuts. Proteins are made of amino acids.
Vitamins: Needed in small amounts for various body functions, like boosting the immune system and helping with energy release. Examples include Vitamin C (in oranges), Vitamin D (from sunlight and some foods), and Vitamin A (in carrots).
Minerals: Also needed in small amounts for various functions, like building strong bones (calcium), carrying oxygen in the blood (iron), and maintaining fluid balance (sodium and potassium).
Dietary Fibre: Important for digestive health. It helps keep things moving smoothly through the digestive system and can help prevent constipation. Found in foods like whole grains, fruits, vegetables, and beans.
Water: Essential for almost all bodily functions. It helps transport nutrients, regulate body temperature, and remove waste. We get water from drinks and many foods.
Importance of Balance: Eating too much or too little of any of these components can lead to health problems. A balanced diet means getting the right amounts of each nutrient.
2. Consequences of Imbalances in Diet
Obesity: Caused by eating too much food, especially foods high in fats and sugars, and not getting enough exercise. The body stores excess energy as fat, leading to being overweight. Obesity can increase the risk of serious health problems like heart disease, type 2 diabetes, and some cancers.
Starvation: Caused by not eating enough food. This means the body doesn't get enough energy or nutrients to function properly. Starvation can lead to weight loss, muscle wasting, weakness, and eventually death.
Deficiency Diseases: Caused by not getting enough of a specific vitamin or mineral. Examples:
Scurvy: Caused by Vitamin C deficiency. Symptoms include bleeding gums, bruising, and slow wound healing.
Rickets: Caused by Vitamin D deficiency. Affects bone development, leading to weak and soft bones, especially in children.
Iron Deficiency Anemia: Caused by not having enough iron. Iron is needed to make red blood cells that carry oxygen. Symptoms include tiredness and weakness.
3. Human Circulatory System
Main Parts: The circulatory system is responsible for transporting blood around the body. It's made up of:
Heart: The pump of the circulatory system. It's a muscular organ that contracts and relaxes to push blood through the blood vessels. Think of it like an engine that drives the blood flow.
Blood Vessels: Tubes that carry blood throughout the body. There are three main types:
Arteries: Carry blood away from the heart. They have thick, elastic walls to withstand the high pressure of blood being pumped from the heart.
Veins: Carry blood back to the heart. They have thinner walls than arteries and contain valves to prevent blood from flowing backwards.
Capillaries: Tiny, thin-walled vessels that connect arteries and veins. They are where exchange of substances (like oxygen, nutrients, and waste products) happens between the blood and body cells.
Blood: The fluid that is transported around the body. It has several components:
Red blood cells: Carry oxygen from the lungs to the body cells. They contain haemoglobin, which binds to oxygen.
White blood cells: Part of the immune system, they fight infection and disease.
Platelets: Help in blood clotting to stop bleeding when you get a cut.
Plasma: The liquid part of the blood, which carries nutrients, hormones, and waste products.
Functions:
Heart: Pumps blood around the body.
Blood Vessels: Provide pathways for blood to travel to all parts of the body and back to the heart.
Blood: Transports:
Oxygen: From lungs to body cells for respiration.
Nutrients: From the digestive system to body cells for energy and growth.
Waste products (like carbon dioxide and urea): From body cells to the lungs and kidneys for removal from the body.
Hormones: Chemical messengers that regulate body functions.
Heat: Helps regulate body temperature.
Immune cells: To fight infection.
4. Bacteria in the Human Digestive System
Importance of Bacteria: While some bacteria can cause disease, many bacteria in our digestive system are beneficial and essential for health. These are often called "gut bacteria" or "gut flora".
Functions of Gut Bacteria:
Digestion: Help to digest food that our bodies can't digest on their own, especially certain types of fibre. They break down complex carbohydrates into simpler substances that we can absorb.
Vitamin Production: Some gut bacteria produce vitamins, like Vitamin K and some B vitamins, which our bodies need.
Protection against harmful bacteria: Good bacteria compete with harmful bacteria for space and resources in the gut, preventing harmful bacteria from taking over and causing illness. They also produce substances that can kill or inhibit harmful bacteria.
Immune System Development: Gut bacteria play a role in training and developing the immune system. They help the immune system learn to distinguish between harmless and harmful substances.
5. Impact of Diet, Exercise, Drugs, and Lifestyle on Body Function
Diet: What we eat has a direct impact on our health. A balanced diet provides the nutrients needed for proper body function. Poor diet (too much sugar, fat, processed foods, not enough fruits and vegetables) can lead to obesity, deficiency diseases, heart disease, type 2 diabetes, and other health problems.
Exercise: Regular physical activity is crucial for health.
Benefits of Exercise: Strengthens the heart and circulatory system, helps maintain a healthy weight, strengthens bones and muscles, improves mood, reduces risk of chronic diseases.
Drugs (including recreational drugs and substance misuse):
Recreational Drugs: Substances taken for pleasure, but many have harmful effects. Examples include alcohol, tobacco (nicotine), cannabis, and illegal drugs like cocaine and heroin.
Substance Misuse: Using drugs in a way that is harmful to your health or well-being. This can lead to addiction and serious health problems.
Effects of Recreational Drugs:
Behaviour: Can alter mood, perception, coordination, and judgment, leading to risky behaviour.
Health: Can damage organs (liver, lungs, brain, heart), increase risk of diseases, and cause addiction.
Life Processes: Can disrupt normal body functions like breathing, heart rate, digestion, and sleep.
Lifestyle: Overall patterns of behaviour and habits. Healthy lifestyle choices include:
Balanced diet.
Regular exercise.
Getting enough sleep.
Managing stress.
Avoiding smoking and excessive alcohol.
Good hygiene.
Maintaining healthy relationships.
Positive Lifestyle Impact: Promotes physical and mental well-being, reduces risk of disease, increases lifespan and quality of life.
6. Effects of Recreational Drugs (including substance misuse)
Behavioural Effects:
Altered mood: Drugs can cause euphoria (extreme happiness), anxiety, depression, or aggression.
Impaired judgment: Drugs can affect decision-making and lead to risky or impulsive actions.
Reduced coordination: Drugs can affect motor skills and balance, increasing the risk of accidents.
Changes in perception: Some drugs can distort senses and cause hallucinations (seeing or hearing things that aren't real).
Addiction: Many recreational drugs are addictive. This means the body becomes dependent on the drug, and stopping it causes withdrawal symptoms. Addiction can control a person's behaviour and life.
Health Effects:
Organ damage: Drugs can damage vital organs like the liver (alcohol), lungs (smoking), brain (many drugs), and heart (stimulants).
Cardiovascular problems: Some drugs increase heart rate and blood pressure, increasing the risk of heart attacks and strokes.
Respiratory problems: Smoking damages the lungs and increases the risk of lung cancer and other respiratory diseases.
Mental health problems: Drug use can trigger or worsen mental health conditions like depression, anxiety, and psychosis.
Weakened immune system: Some drugs can weaken the immune system, making the body more vulnerable to infections.
Overdose: Taking too much of a drug can be fatal.
Life Process Effects:
Disrupted sleep patterns: Drugs can interfere with sleep, leading to insomnia or excessive sleepiness.
Changes in appetite and digestion: Some drugs can suppress appetite, while others can increase it. Drug use can also disrupt digestion and cause stomach problems.
Hormonal imbalances: Some drugs can affect hormone production and regulation.
Impact on reproduction: Drug use can affect fertility and pregnancy.
7. Good Hygiene and Health
Hygiene: Practices that promote cleanliness and health.
Importance of Good Hygiene: Helps to prevent the spread of germs (bacteria, viruses, fungi, parasites) that can cause infections and diseases.
Key Hygiene Practices:
Handwashing: Washing hands with soap and water, especially after using the toilet, before eating, after being in public places, and after touching animals. This removes germs that can cause illness.
Bathing/Showering Regularly: Keeps the body clean and removes dirt and sweat that can harbour germs.
Dental hygiene: Brushing teeth twice a day and flossing helps remove bacteria and food particles that can cause tooth decay and gum disease.
Food hygiene: Washing fruits and vegetables, cooking food properly, storing food safely to prevent food poisoning.
Respiratory hygiene: Covering mouth and nose when coughing or sneezing to prevent spreading germs through the air.
Clean clothing: Wearing clean clothes helps prevent skin infections and reduces the spread of germs.
Hygiene and Health Connection: Good hygiene is a simple but very effective way to stay healthy and reduce the risk of getting sick and spreading illnesses to others.
8. Nutrition for Animals (including humans)
Need for Nutrition: All animals, including humans, need the right types and amounts of nutrition to survive and thrive. Nutrition provides:
Energy: To power all body processes like movement, growth, breathing, and thinking.
Building blocks: To build and repair tissues, grow, and develop.
Regulation of body processes: Vitamins and minerals are essential for regulating various chemical reactions and functions in the body.
"Right Types" of Nutrition: Animals need a variety of nutrients, just like humans. The specific needs vary depending on the type of animal, its age, size, and activity level.
Herbivores (plant-eaters): Need diets rich in carbohydrates and fibre from plants.
Carnivores (meat-eaters): Need diets rich in protein and fats from other animals.
Omnivores (eat both plants and animals): Need a balanced diet including both plant and animal matter.
"Right Amount" of Nutrition: Getting too little or too much nutrition can be harmful.
Undernutrition: Not getting enough food or nutrients can lead to starvation, deficiency diseases, and stunted growth.
Overnutrition: Eating too much food, especially high-calorie foods, can lead to obesity and related health problems.
Chapter B3: Living together – food and ecosystems
1. Plant and Animal Cells
Cells as Building Blocks: All living things are made of cells. Cells are like tiny building blocks, the smallest units of life that can carry out all life processes.
Similarities between Plant and Animal Cells: Both plant and animal cells have some common parts:
Cell Membrane: The outer boundary of the cell. It controls what enters and leaves the cell. Imagine it like a gatekeeper.
Nucleus: The control center of the cell. It contains the genetic material (DNA) which carries instructions for how the cell works. Think of it as the brain of the cell.
Cytoplasm: A jelly-like substance that fills the cell. It's where many chemical reactions happen and where the other cell parts are located.
Differences between Plant and Animal Cells: Plant cells have some parts that animal cells do not:
Cell Wall: A rigid outer layer outside the cell membrane in plant cells. It provides support and gives the plant cell a fixed shape. Animal cells do not have a cell wall. Think of it like a sturdy box around the plant cell.
Chloroplasts: Found in plant cells, especially in leaves. Chloroplasts contain chlorophyll, which is a green pigment that absorbs light energy for photosynthesis. Animal cells do not have chloroplasts.
Large Vacuole: Plant cells usually have a large, central vacuole that stores water, nutrients, and waste. It also helps to keep the cell firm. Animal cells may have small vacuoles, but not a large central one.
2. Photosynthesis
Making Food: Photosynthesis is the process by which plants make their own food. It's how they get energy to grow and live. Animals cannot make their own food; they need to eat plants or other animals.
Organisms that Photosynthesize: Plants, algae, and some bacteria can photosynthesize. They are called producers because they produce their own food.
Location of Photosynthesis: Photosynthesis happens inside chloroplasts, which are found in plant cells, especially in the leaves. Chloroplasts contain chlorophyll, the green pigment that captures light energy.
Reactants and Products of Photosynthesis (Word Summary):
Reactants (what is needed):
Carbon Dioxide: Taken in from the air through tiny holes in leaves called stomata.
Water: Absorbed from the soil through the roots.
Light: Energy from the sun, captured by chlorophyll.
Products (what is made):
Glucose (Sugar): The food (energy) that plants make. It's a type of carbohydrate.
Oxygen: Released into the air through stomata. This is the oxygen we breathe!
Word Equation for Photosynthesis:
Carbon Dioxide + Water + Light Energy → Glucose + Oxygen
Light is Required: Photosynthesis cannot happen without light. Plants need sunlight (or artificial light) to provide the energy for the process. Photosynthesis happens during the day when there is light.
3. Adaptations of Leaves for Photosynthesis
Leaves as Photosynthetic Organs: Leaves are the main organs of photosynthesis in most plants. They are specially adapted to capture sunlight and take in carbon dioxide.
Adaptations of Leaves:
Large Surface Area: Leaves are broad and flat, providing a large surface area to capture as much sunlight as possible.
Thin: Leaves are thin so that carbon dioxide can quickly diffuse into the cells and light can penetrate to the chloroplasts.
Chloroplasts in Cells: Leaf cells are packed with chloroplasts, especially in the upper layers, to maximize light capture.
Veins: Leaves have veins that contain xylem and phloem.
Xylem: Tubes that transport water from the roots to the leaves, needed for photosynthesis.
Phloem: Tubes that transport glucose (food) made in photosynthesis from the leaves to other parts of the plant (like roots, stems, fruits, flowers) for growth and storage.
Stomata: Tiny pores (holes) on the lower surface of leaves.
Function of Stomata:
Gas Exchange: Stomata allow carbon dioxide to enter the leaf for photosynthesis and oxygen (a product of photosynthesis) to exit.
Water Loss (Transpiration): Water vapour also escapes through stomata. Plants need to balance gas exchange with water loss.
Guard Cells: Special cells around each stoma that can open and close the stomata to control gas exchange and water loss.
4. Roots and Water/Mineral Uptake
Roots Anchor Plants and Absorb: Roots have two main functions:
Anchoring: Roots anchor the plant firmly in the ground, preventing it from being blown away by wind or washed away by rain.
Absorption: Roots absorb water and mineral salts (nutrients) from the soil. These are essential for plant growth and photosynthesis.
How Roots Absorb Water and Minerals:
Root Hair Cells: Roots have tiny root hair cells that greatly increase the surface area for absorption.
Water Absorption: Water moves into root hair cells from the soil by osmosis. Osmosis is the movement of water from an area of high water concentration (in the soil) to an area of low water concentration (inside the root hair cells) across a partially permeable membrane.
Mineral Absorption: Minerals are dissolved in water in the soil. They are absorbed by root hair cells by diffusion and active transport.
Diffusion: Movement of particles from an area of high concentration to an area of low concentration. Mineral concentration is usually higher in the soil than in root hair cells, so minerals move in by diffusion.
Active Transport: Sometimes, mineral concentration is lower in the soil than in root hair cells. In this case, plants use energy to actively pump minerals into root cells against the concentration gradient.
5. Diffusion
Movement of Particles: Diffusion is the movement of particles (atoms, molecules, ions) from an area of high concentration to an area of low concentration. It's a passive process, meaning it doesn't require energy input.
Molecules of a Solute in a Solvent: If you put sugar (solute) in water (solvent), the sugar molecules will spread out and mix evenly in the water. This is diffusion.
Diffusion Across Cell Membranes: Cell membranes are partially permeable, meaning they allow some substances to pass through but not others. Small molecules like oxygen, carbon dioxide, and water can move across cell membranes by diffusion.
Importance of Diffusion in Living Organisms:
Gas Exchange: Oxygen moves from the lungs into the blood, and carbon dioxide moves from the blood into the lungs by diffusion. In leaves, carbon dioxide enters and oxygen exits through stomata by diffusion.
Nutrient Uptake and Waste Removal: Nutrients move from the small intestine into the blood, and waste products move from cells into the blood by diffusion.
6. Feeding Relationships
Animals Get Food from Plants (or other animals that ate plants): Animals cannot make their own food like plants. They are consumers - they get energy by eating other organisms.
Herbivores: Animals that eat plants. Examples: cows, rabbits, caterpillars. They are primary consumers because they directly eat producers (plants).
Carnivores: Animals that eat other animals (meat). Examples: lions, sharks, spiders. They can be secondary consumers (eat herbivores) or tertiary consumers (eat other carnivores).
Omnivores: Animals that eat both plants and animals. Examples: humans, bears, chickens.
Producers and Consumers:
Producers: Organisms that make their own food, usually by photosynthesis (like plants and algae). They form the base of food chains.
Consumers: Organisms that eat other organisms to get energy. They depend on producers directly or indirectly for food. Herbivores, carnivores, and omnivores are all consumers.
7. Populations, Communities, and Ecosystems
Population: All the individuals of the same type (same species) living in the same place at the same time. Examples: all the oak trees in a forest, all the rabbits in a field, all the humans in a city.
Community: All the interacting populations of different species living in the same ecosystem. It's all the living organisms in an area. Examples: all the plants, animals, fungi, and bacteria in a forest.
Ecosystem: A community of living organisms (biotic factors) interacting with each other and with their non-living environment (abiotic factors) in a particular area. Abiotic factors include things like water, air, soil, sunlight, temperature, and climate. Examples: a forest, a pond, a grassland, a desert.
8. Food Chains and Food Webs
Food Chains: Simple models that show the flow of energy in an ecosystem. They show "who eats whom".
Arrows show the direction of energy flow: From the organism being eaten to the organism that eats it.
Example Food Chain:
Grass → Rabbit → Fox
(Producer) → (Primary Consumer/Herbivore) → (Secondary Consumer/Carnivore)
Food Webs: More complex models that show the interconnected food chains in an ecosystem. Most animals eat more than one type of food, and are eaten by more than one type of predator. Food webs show these complex feeding relationships.
Food webs are more realistic than food chains because they show that ecosystems are interconnected.
Trophic Levels: Each step in a food chain or food web is called a trophic level.
Trophic Level 1: Producers (plants)
Trophic Level 2: Primary consumers (herbivores)
Trophic Level 3: Secondary consumers (carnivores that eat herbivores)
Trophic Level 4 (and higher): Tertiary consumers, quaternary consumers, etc. (carnivores that eat other carnivores)
9. Interdependence in a Community
Organisms Depend on Each Other: Organisms in a community are interdependent, meaning they rely on each other in various ways for survival.
Food Webs (Interdependence for Food): Food webs show how organisms are linked through feeding relationships. Changes in one population can affect other populations in the food web.
Breakdown and Cycling of Substances (Decomposers):
Decomposers: Organisms like bacteria and fungi that break down dead plants and animals and waste materials.
Nutrient Cycling: Decomposers release nutrients (like minerals) back into the soil. These nutrients are then taken up by plants, and the cycle continues. This cycling of nutrients is essential for maintaining a healthy ecosystem.
Animals as Pollinators:
Pollination: Transfer of pollen from the stamen to the pistil of a flower, needed for plant fertilization.
Pollinators: Animals (like bees, butterflies, birds, bats) that help to carry pollen from one flower to another.
Mutualism: Pollination is an example of mutualism, a type of interdependence where both organisms benefit. The plant gets pollinated, and the pollinator gets food (nectar, pollen).
10. Ecosystem Changes and Survival
Ecosystems are Dynamic: Ecosystems are constantly changing. Changes can be natural (like seasonal changes, natural disasters) or caused by humans (like pollution, deforestation, climate change).
Impact of Changes: Changes in an ecosystem can affect the survival of individuals and populations.
Habitat Loss: If a habitat is destroyed (e.g., deforestation), organisms that live there lose their homes and food sources. They may have to move, adapt, or they may die out.
Pollution: Pollution can make the environment toxic, harming or killing organisms.
Climate Change: Changes in temperature and rainfall patterns can affect which organisms can survive in an ecosystem.
Introduction of Invasive Species: New species introduced into an ecosystem can compete with native species for resources, sometimes leading to the decline or extinction of native populations.
Survival and Adaptation: Organisms need to be able to adapt to changes in their environment to survive. If changes are too rapid or too drastic, some species may not be able to adapt and may become endangered or extinct.
Chapter B4: Using food and controlling growth
1. Aerobic and Anaerobic Respiration and Fermentation
What is Respiration? Respiration is how living things release energy from food. All living organisms need energy to live, grow, move, and do everything they do. Think of it like burning fuel to power a car, but in living things, the 'fuel' is food (like glucose).
Aerobic Respiration (With Oxygen): This is the most common type of respiration. It happens when there is enough oxygen available.
Where it happens: In the cells of most living organisms, including animals, plants, and many microorganisms.
What is needed (Reactants):
Glucose (Sugar): This comes from the food we eat (or that plants make in photosynthesis).
Oxygen: We breathe in oxygen from the air.
What is produced (Products):
Carbon Dioxide: This is a waste gas that we breathe out.
Water: Also a waste product, but it's useful for the body.
Energy: This is the important product! It's released for the organism to use.
Word Summary of Aerobic Respiration:
Glucose + Oxygen → Carbon Dioxide + Water + Energy
Anaerobic Respiration (Without Oxygen): This type of respiration happens when there is not enough oxygen available. It's less efficient than aerobic respiration, meaning it releases less energy.
When it happens:
In animals: During vigorous exercise when muscles are working hard and can't get oxygen quickly enough.
In some microorganisms: Some microorganisms, like yeast and some bacteria, can survive and respire without oxygen all the time.
What is needed (Reactants):
Glucose (Sugar): Same as in aerobic respiration.
What is produced (Products) in Animals:
Lactic Acid: This is a waste product that can build up in muscles and cause them to feel tired and ache (muscle fatigue).
Energy: Less energy is released compared to aerobic respiration.
Word Summary of Anaerobic Respiration in Animals:
Glucose → Lactic Acid + Energy (less energy than aerobic)
Fermentation in Microorganisms (e.g., Yeast): This is a type of anaerobic respiration that happens in some microorganisms like yeast and bacteria.
Example: Yeast Fermentation (Alcoholic Fermentation): Yeast is used to make bread and alcoholic drinks.
What is needed (Reactants):
Glucose (Sugar): Yeast gets sugar from grains or fruits.
What is produced (Products):
Carbon Dioxide: This is what makes bread rise and gives bubbles to drinks like beer and sparkling wine.
Ethanol (Alcohol): This is the alcohol in alcoholic drinks.
Energy: A small amount of energy is released.
Word Summary of Fermentation in Yeast (Alcoholic Fermentation):
Glucose → Carbon Dioxide + Ethanol + Energy (very little energy)
3. Human Digestive System
Purpose of the Digestive System: To break down large, complex food molecules into smaller, simpler molecules that the body can absorb and use for energy, growth, and repair.
Tissues and Organs of the Human Digestive System: The digestive system is a long tube starting at the mouth and ending at the anus. It includes several organs:
Mouth:
Function: Ingestion (taking food in), mechanical digestion (chewing food into smaller pieces), chemical digestion starts (saliva contains enzymes to break down starch).
Adaptations: Teeth for chewing, tongue to mix food with saliva, salivary glands to produce saliva.
Esophagus (Gullet):
Function: Tube that carries food from the mouth to the stomach.
Adaptations: Muscular walls to squeeze food down (peristalsis).
Stomach:
Function: Mechanical digestion (churning food), chemical digestion (starts breaking down proteins using stomach acid and enzymes).
Adaptations: Muscular walls to churn food, produces stomach acid (hydrochloric acid) to kill bacteria and help enzymes work, produces enzymes (like pepsin) to digest proteins, has a mucus lining to protect itself from the acid.
Small Intestine:
Function: Main site of chemical digestion and absorption of nutrients into the bloodstream. Digestion of carbohydrates, proteins, and fats is completed here.
Adaptations: Very long (increases surface area for absorption), inner lining folded into villi and microvilli (even more surface area), produces enzymes, receives enzymes and bile from the pancreas and liver, thin walls for easy absorption into blood capillaries.
Large Intestine (Colon):
Function: Absorption of water from undigested food, formation of feces.
Adaptations: Long, muscular walls to move undigested material, absorbs water back into the body.
Rectum:
Function: Storage of feces before removal.
Anus:
Function: Egestion (removal of feces from the body).
Accessory Organs (Help with Digestion, but Food Doesn't Pass Through Them):
Salivary Glands: Produce saliva containing enzymes to start digesting starch in the mouth.
Pancreas: Produces digestive enzymes that are released into the small intestine to digest carbohydrates, proteins, and fats. Also produces hormones like insulin to regulate blood sugar.
Liver: Produces bile, which helps to digest fats in the small intestine. Bile is stored in the gallbladder before being released.
Gallbladder: Stores and concentrates bile produced by the liver.
4. Chemical Digestion and Enzymes
Chemical Digestion: Breaking down large food molecules into smaller ones using chemicals called enzymes.
Enzymes as Biological Catalysts: Enzymes are special proteins that speed up chemical reactions in the body. In digestion, enzymes help to break down large food molecules into smaller ones much faster than they would break down on their own.
Enzymes in the Digestive System:
Salivary Amylase (in saliva): Starts to digest starch (a carbohydrate) into sugars in the mouth.
Pepsin (in stomach acid): Digests proteins into smaller peptides in the stomach.
Enzymes from Pancreas (released into small intestine):
Amylase: Digests remaining starch into sugars.
Proteases (e.g., trypsin): Digest proteins into amino acids.
Lipases: Digest fats (lipids) into fatty acids and glycerol.
Enzymes from Small Intestine Lining: Further break down sugars and peptides into even smaller molecules (like glucose and amino acids) ready for absorption.
Simple Terms: Think of enzymes as tiny "scissors" or "helpers" that cut up big food molecules into smaller pieces that the body can use.
5. Importance of Bacteria in the Human Digestive System
(Already covered in detail in the previous response, but important to reiterate): Many bacteria live in our large intestine. These are "good bacteria" or "gut flora."
Functions of Gut Bacteria:
Help with Digestion: They digest some food that we can't digest ourselves, especially certain types of fibre.
Produce Vitamins: They make some vitamins that our bodies need, like Vitamin K and some B vitamins.
Protect Against Harmful Bacteria: They compete with bad bacteria and help prevent infections.
Help Train the Immune System: They help our immune system learn to recognize and fight off harmful germs.
6. Transport of Nutrients and Water in Animals (including Humans)
Need for Transport: After digestion, the small, soluble food molecules (nutrients) and water need to be transported from the digestive system to all the cells in the body where they are needed. Waste products also need to be transported away from cells to organs that can remove them.
Circulatory System for Transport: In animals (including humans), the circulatory system is the main transport system.
Blood: The transport medium. It carries nutrients, water, oxygen, waste products, hormones, etc.
Blood Vessels (Arteries, Veins, Capillaries): Tubes that blood flows through.
Heart: The pump that keeps the blood circulating.
Absorption of Nutrients and Water in the Small Intestine:
Villi and Microvilli: The lining of the small intestine is folded into villi and microvilli, which greatly increase the surface area for absorption.
Absorption into Blood Capillaries: Small, digested food molecules (like glucose, amino acids, fatty acids, glycerol, vitamins, minerals) and water pass through the thin walls of the villi into blood capillaries.
Transport in Blood: The blood in the capillaries in the villi carries these nutrients and water away from the small intestine.
Water Absorption in Large Intestine: Water is also absorbed in the large intestine from the undigested food material, and this water also enters the bloodstream to be transported around the body.
Delivery to Body Cells: The blood circulates around the body, and in capillaries near body cells, nutrients, water, and oxygen move out of the blood into the cells by diffusion. Waste products from cells move into the blood to be carried away for removal.
Chapter B5: The human body – staying alive
1. Hierarchical Organisation of Multicellular Organisms
Multicellular Organisms: Living things made of many cells (like humans, animals, and plants). Think of them as complex structures built from tiny units.
Hierarchy: A way of organizing things from the simplest to the most complex, with each level building upon the previous one. In living things, this organization is:
Cells: The basic building blocks of life. Everything living is made of cells. They are tiny units that carry out life processes. Different cells have different jobs. Example: Muscle cells, nerve cells, skin cells.
Tissues: Groups of similar cells working together to perform a specific job. Example: Muscle tissue (for movement), nervous tissue (for communication), epithelial tissue (covering surfaces like skin).
Organs: Structures made of different tissues working together to perform a larger job. Example: Heart (pumps blood), lungs (gas exchange), stomach (digestion), brain (control center).
Systems (Organ Systems): Groups of organs working together to perform major functions in the body. Example: Digestive system (digests food), circulatory system (transports blood), respiratory system (gas exchange), nervous system (communication and control).
Organism: A complete living being made up of all the organ systems working together. Example: A human, a cat, a tree.
Analogy: Think of building with LEGOs:
Cells: Like individual LEGO bricks.
Tissues: Like small structures built from LEGO bricks (e.g., a LEGO wall).
Organs: Like larger structures built from LEGO tissues (e.g., a LEGO room).
Systems: Like sections of a LEGO house made of LEGO rooms (e.g., kitchen section, bedroom section).
Organism: The whole LEGO house made of all the sections.
2. Basic Parts of the Human Body
Identifying and Naming: Learners should be able to point to, name, and draw/label these basic parts:
Head: Top part of the body, contains the brain, eyes, ears, nose, and mouth.
Hair: Covers the scalp (top of the head), provides some warmth and protection.
Face: Front part of the head, includes eyes, nose, mouth, cheeks, and chin.
Eyes: Organs of sight, allow us to see.
Ears: Organs of hearing, allow us to hear and help with balance.
Nose: Organ of smell and part of the respiratory system, allows us to breathe and smell.
Mouth: Used for eating, speaking, and breathing. Contains teeth and tongue.
Neck: Connects the head to the torso, allows head movement.
Shoulders: Where arms attach to the torso.
Arms: Upper limbs, used for reaching, grasping, and manipulating objects.
Hands: At the end of arms, used for fine motor skills, touching, and holding. Include fingers and thumbs.
Chest: Upper part of the torso, contains lungs and heart.
Stomach/Abdomen: Middle part of the torso, contains digestive organs.
Back: Rear part of the torso, provides support.
Legs: Lower limbs, used for standing, walking, running, and jumping.
Feet: At the end of legs, used for standing and walking. Include toes.
Drawing and Labelling: Simple diagrams of the human body can be used, and learners should be able to label these parts on a drawing or diagram.
3. Function of Muscles
Muscles and Movement: Muscles are tissues that allow the body to move. They work by contracting (getting shorter) and relaxing (getting longer).
Basic Function: Muscles cause movement. They help us:
Move our body parts: Walking, running, jumping, waving hands, nodding head, blinking eyes, smiling.
Move things inside our body: Heart muscle pumps blood, muscles in the digestive system move food along.
Maintain posture: Muscles help us stand up straight and keep our balance.
Generate heat: Muscle activity produces heat, which helps keep our body warm.
Types of Muscles (Simplified):
Skeletal Muscles: Attached to bones. We can consciously control them to move our limbs and body (voluntary muscles). Example: Muscles in arms and legs.
Smooth Muscles: Found in the walls of internal organs like the stomach, intestines, and blood vessels. They work automatically without us thinking about it (involuntary muscles). Example: Muscles in the digestive system that move food along.
Cardiac Muscle: Found only in the heart. It's a special type of muscle that contracts rhythmically to pump blood around the body (involuntary muscle).
Muscles Work in Pairs: Skeletal muscles often work in pairs to produce movement at joints. When one muscle contracts, its partner relaxes. Example: Biceps and triceps in the arm work together to bend and straighten the elbow.
4. Tissues and Organs of the Human Digestive System
(Covered in detail in the previous response, but important to reiterate and simplify): The digestive system breaks down food so the body can absorb nutrients.
Main Organs:
Mouth: Where food enters, chewing starts.
Esophagus (Gullet): Tube that food travels down to the stomach.
Stomach: Churns food and mixes it with stomach acid.
Small Intestine: Main place where food is digested and nutrients are absorbed into the blood.
Large Intestine (Colon): Absorbs water, and waste is formed.
Anus: Where waste (feces) leaves the body.
Adaptations to Function (Simplified):
Mouth (Teeth): For chewing and breaking down food into smaller pieces.
Stomach (Muscular Walls): For churning and mixing food.
Small Intestine (Long and Folded): Large surface area for absorbing nutrients.
Small Intestine (Thin Walls): For easy passage of nutrients into the blood.
5. Basic Structures and Functions of the Gas Exchange System in Humans
Gas Exchange: The process of taking in oxygen and getting rid of carbon dioxide. This is essential for respiration (releasing energy from food).
Organs of the Gas Exchange System (Respiratory System):
Nose and Mouth: Air enters the body through the nose and mouth.
Trachea (Windpipe): Tube that carries air from the nose/mouth to the lungs.
Bronchi: The trachea splits into two bronchi, one for each lung.
Lungs: Main organs of gas exchange. They contain millions of tiny air sacs called alveoli.
Alveoli: Tiny air sacs in the lungs. This is where gas exchange actually happens.
Functions:
Taking in Oxygen: We breathe in air that contains oxygen. Oxygen is needed for respiration in cells.
Getting rid of Carbon Dioxide: Respiration produces carbon dioxide as a waste product. We need to breathe out carbon dioxide to get rid of it.
Adaptations for Gas Exchange in Alveoli:
Large Surface Area: Millions of alveoli provide a huge surface area for gas exchange.
Thin Walls: Alveoli and capillaries (tiny blood vessels around alveoli) have very thin walls, so gases can easily diffuse across.
Good Blood Supply: Alveoli are surrounded by many capillaries, ensuring a good blood supply to carry oxygen away and bring carbon dioxide to be removed.
Moist Surface: The lining of the alveoli is moist, which helps gases dissolve and diffuse more easily.
6. Mechanism of Breathing
Breathing (Ventilation): The process of moving air in and out of the lungs. It has two main parts:
Inhalation (Breathing In):
Diaphragm: A large, dome-shaped muscle under the lungs, contracts and flattens.
Rib Cage: Muscles between the ribs contract, pulling the rib cage upwards and outwards.
Chest Volume: Increases.
Pressure in Lungs: Decreases (becomes lower than air pressure outside the body).
Air Movement: Air rushes into the lungs from outside (because air moves from high pressure to low pressure).
Exhalation (Breathing Out):
Diaphragm: Relaxes and moves back up into its dome shape.
Rib Cage: Muscles between the ribs relax, and the rib cage moves downwards and inwards.
Chest Volume: Decreases.
Pressure in Lungs: Increases (becomes higher than air pressure outside the body).
Air Movement: Air is pushed out of the lungs to the outside (because air moves from high pressure to low pressure).
Pressure Model for Gas Movement: Gases (like air, oxygen, carbon dioxide) move from areas of high pressure to areas of low pressure. Breathing works by changing the pressure in our chest and lungs to create a pressure difference between the air inside and outside the lungs, causing air to move in or out.
7. Transport of Nutrients and Water Within Animals, Including Humans
(Covered in detail in the previous response, but simplify for this context): Nutrients and water from digested food need to get to all parts of the body.
Circulatory System (Transport System): The circulatory system is like a transport network in the body.
Blood: Carries nutrients and water (and oxygen, etc.).
Blood Vessels (Arteries, Veins, Capillaries): Like roads and pathways for the blood.
Heart: The pump that keeps the blood moving around.
Outline of Transport:
Absorption: Nutrients and water are absorbed from the digestive system (mainly small intestine) into the blood.
Circulation: The heart pumps blood through blood vessels all around the body.
Delivery: Blood delivers nutrients and water to all cells in the body.
Waste Removal: Blood also picks up waste products from cells and transports them to organs that remove waste (like lungs and kidneys).
8. Main Parts of the Human Circulatory System
(Covered in previous responses, but reiterate key parts):
Heart: The muscular pump.
Blood Vessels:
Arteries: Carry blood away from the heart.
Veins: Carry blood back to the heart.
Capillaries: Tiny vessels where exchange happens between blood and cells.
Blood: The fluid that is transported.
9. Functions of the Heart, Blood Vessels, and Blood
Heart:
Pumping Blood: The heart's main function is to pump blood around the body. It beats continuously to keep blood circulating.
Receiving and Sending Blood: The heart receives deoxygenated blood from the body and pumps it to the lungs to get oxygen. It also receives oxygenated blood from the lungs and pumps it out to the rest of the body.
Blood Vessels:
Arteries: Carry oxygenated blood (except for the pulmonary artery) away from the heart to the body organs and tissues. They have strong, elastic walls to handle high pressure.
Veins: Carry deoxygenated blood (except for the pulmonary vein) back to the heart from the body organs and tissues. They have thinner walls and valves to prevent backflow.
Capillaries: Connect arteries and veins. They are very thin and narrow, allowing exchange of substances (oxygen, nutrients, carbon dioxide, waste) between the blood and body cells.
Blood:
Transport: Blood transports:
Oxygen: From lungs to body cells.
Carbon Dioxide: From body cells to lungs.
Nutrients: From digestive system to body cells.
Waste Products: From body cells to excretory organs (like kidneys).
Hormones: Chemical messengers.
Heat: Helps regulate body temperature.
Immune Cells: To fight infection.
10. Part of the Body Associated with Each Sense
Five Senses: Humans have five main senses that help us understand the world around us:
Sight (Vision):
Organ: Eyes.
Function: To see objects, colors, light, and movement.
Hearing (Audition):
Organ: Ears.
Function: To hear sounds and help with balance.
Smell (Olfaction):
Organ: Nose.
Function: To detect smells and odors.
Taste (Gustation):
Organ: Tongue.
Function: To detect different tastes (sweet, sour, salty, bitter, umami). Taste buds on the tongue are the sensory receptors.
Touch (Tactition):
Organ: Skin.
Function: To feel pressure, temperature, pain, and texture. Receptors in the skin detect these sensations.
Chapter B6: Life on Earth – past, present and future
1. Variety of Organisms and Environments
Many Different Types of Organisms: The world is full of an amazing variety of living things, called organisms. This includes:
Plants: Trees, flowers, grasses, ferns, mosses, etc.
Animals: Mammals (like humans, cats, dogs), birds, reptiles, amphibians, fish, insects, worms, snails, etc.
Microorganisms: Things too small to see with just your eyes, like bacteria, fungi, and algae.
Different Environments: Organisms live in many different places, called environments or habitats.
Land Environments (Terrestrial): Forests, grasslands, deserts, mountains, farms, gardens, cities.
Water Environments (Aquatic): Oceans, rivers, lakes, ponds, swamps, coral reefs.
Even extreme environments: Hot deserts, icy polar regions, deep oceans.
Similarities and Differences Between Organisms: Even though there are so many different types of organisms, they also have some things in common, and many differences.
Similarities: All living things:
Are made of cells.
Need food, water, and air (or gases).
Can grow.
Can reproduce (make more of their own kind).
Can respond to their surroundings.
Differences: Organisms differ in:
Size (from tiny bacteria to giant whales).
Shape and appearance.
How they get food (some make their own, others eat other organisms).
Where they live and how they are suited to their environment.
2. Classification of Living Organisms
Grouping Organisms: Scientists group living things to make it easier to study and understand them. This is called classification.
Ways to Classify: Organisms can be grouped based on their:
Similarities: Things they have in common, like body parts, how they move, what they eat, how they reproduce.
Differences: Things that make them different from each other.
Variety of Ways to Classify: There are many ways to group organisms. For example, we can group animals by:
What they eat: Herbivores (plant-eaters), carnivores (meat-eaters), omnivores (eat both).
Where they live: Land animals, water animals, animals that can fly.
If they have a backbone: Vertebrates (with backbone), invertebrates (without backbone).
By their body covering: Animals with fur, feathers, scales, or shells.
3. Classification Keys
What are Classification Keys? Tools used to help identify and classify organisms. They are like a series of questions that you answer to narrow down what an organism could be.
How to Use a Key:
Start at the beginning of the key (usually question 1).
Read the question and choose the answer that best describes the organism you are trying to identify.
Follow the instructions after your answer, which will lead you to another question or tell you the name of the organism.
Keep going until you reach the end and identify the organism.
Example of a Simple Key (for Animals):
Does the animal have feathers?
Yes: It is likely a bird. Go to question 2.
No: Go to question 3.
Can it swim underwater?
Yes: Likely a penguin.
No: Likely a sparrow.
Does it have fur or hair?
Yes: Likely a mammal. Go to question 4.
No: Likely an insect.
Does it eat only plants?
Yes: Likely a rabbit.
No: Likely a dog.
4. Organisms Change Over Time and Fossils
Living Things Change Over Time (Evolution): Life on Earth has changed a lot over millions of years. Organisms living today are different from those that lived long ago. This process of change over time is called evolution.
Fossils as Evidence of Past Life: Fossils are the preserved remains or traces of organisms that lived in the past. They are like snapshots of life from millions of years ago.
Types of Fossils: Bones, shells, footprints, impressions of leaves or insects in rock, insects trapped in amber.
Fossils tell us:
What kinds of organisms lived in the past.
That organisms have changed over time.
About environments from long ago.
Millions of Years Ago: Fossils show us that life on Earth is very old, and that organisms have been evolving for millions of years. Some fossils are millions or even billions of years old!
5. Habitats and Adaptations
Habitats: The natural environment where an organism lives. It provides everything an organism needs to survive, like food, water, shelter, and space. Examples: Forest habitat, desert habitat, pond habitat.
Adaptations: Special features or characteristics that help an organism survive in its habitat. Adaptations can be:
Physical Adaptations (Body Features): Examples: Camels have humps to store fat (energy) and long eyelashes to protect eyes from sand in the desert; Fish have fins for swimming and gills for breathing in water.
Behavioral Adaptations (Actions): Examples: Birds migrate to warmer places in winter to find food; Desert animals are often active at night to avoid the heat of the day.
Organisms are Adapted to their Habitats: Organisms are suited to live in their specific habitats because of their adaptations. If an organism is moved to a habitat it is not adapted to, it may struggle to survive.
6. Variation Within a Species
Species: A group of organisms that are very similar to each other and can breed together to produce offspring that can also reproduce. Example: All humans are part of the human species; All domestic dogs are part of the dog species.
Variation: Differences between individuals within the same species. Even though individuals of the same species are similar, they are not exactly identical. Examples in humans: Different hair color, eye color, height, skin tone. Examples in dogs: Different fur color, size, ear shape.
Continuous Variation: Variation that can take any value within a range. There are many possible values between two extremes. Examples: Height, weight, shoe size, skin color in humans. Often measured and shown on graphs as a range.
Discontinuous Variation: Variation where individuals fall into distinct categories or groups. There are only a limited number of possible values, with no values in between. Examples: Eye color categories (blue, brown, green), blood groups (A, B, AB, O), gender (male/female in humans). Often shown in bar charts or pie charts.
7. Variation, Competition, and Natural Selection
Competition: Living things need resources to survive, like food, water, space, and mates. Organisms in a habitat often compete with each other for these limited resources.
Competition within a species: Individuals of the same species compete with each other. Example: Two foxes competing for the same rabbit to eat.
Competition between different species: Different species may also compete if they need the same resources. Example: Foxes and hawks competing for small rodents.
Variation and Success in Competition: Because of variation, some individuals in a species are better suited to their environment than others. These individuals are more likely to:
Survive: They are better at finding food, avoiding predators, or resisting diseases.
Reproduce: They are more likely to live long enough and be healthy enough to find mates and have offspring.
Natural Selection ("Survival of the Fittest"): The process where individuals with advantageous (helpful) variations are more likely to survive and reproduce, passing on those advantageous variations to their offspring. Over many generations, this can lead to changes in the species as a whole.
Example: Imagine rabbits in a field. Some rabbits are faster than others. Faster rabbits are more likely to escape foxes (predators) and survive to have babies. Speed (variation) helps in competition for survival. Over time, there might be more faster rabbits than slower rabbits in the population because faster rabbits are more likely to pass on their genes for speed.
"Nature Selects": The environment "selects" which variations are most helpful. It's not a conscious choice, but rather a natural process where the environment favors certain traits.
8. Evolution of Species
Evolution: The gradual change in the characteristics of species over long periods of time. Natural selection is the main driving force behind evolution.
Variation, Adaptation, Competition, and Natural Selection lead to Evolution:
Variation: Provides the raw material for evolution. Without variation, there would be nothing for natural selection to act upon.
Adaptation: Helpful variations that make organisms better suited to their environment.
Competition: Creates the "struggle for survival" where only the best-adapted individuals are likely to succeed.
Natural Selection: Favors advantageous adaptations, allowing them to become more common in a population over generations.
Species Change Over Time: Over very long periods, natural selection can cause species to change so much that they become new species. This is how life on Earth has become so diverse.
9. Environmental Changes and Extinction
Environments Change: Environments are not constant. They can change due to:
Natural Events: Climate change (ice ages, warming periods), volcanic eruptions, earthquakes, floods, droughts, fires.
Human Activities: Pollution, deforestation, habitat destruction, introduction of invasive species, climate change caused by burning fossil fuels.
Impact of Environmental Change: If the environment changes, organisms may be less well adapted to compete and survive.
Less Successful Competition: Adaptations that were once helpful may become less useful, or even harmful, in a changed environment.
Reduced Reproduction: Organisms that are less well adapted may struggle to find food, shelter, or mates, and may not be able to reproduce successfully.
Extinction: If a species cannot adapt to a major environmental change, it may die out completely. This is called extinction. Extinction is a natural process, but human activities are causing extinctions to happen much faster than they normally would.
10. Importance of Biodiversity and Conservation
Biodiversity: The variety of all living things on Earth. It includes the variety of species, the variety of genes within species, and the variety of ecosystems.
Why is Biodiversity Important?
Ecosystem Stability: Diverse ecosystems are more stable and resilient. They are better able to cope with changes and disasters.
Food Webs: Biodiversity supports complex food webs. If one species is lost, it can affect many others.
Resources for Humans: We rely on biodiversity for food, medicine, materials (wood, fibers), clean air and water, pollination of crops, and many other essential things.
Beauty and Enjoyment: Nature and wildlife are beautiful and enrich our lives.
Ethical Reasons: Many people believe we have a responsibility to protect other species and the natural world.
Threats to Biodiversity: Human activities are causing biodiversity loss at an alarming rate. Main threats include:
Habitat Destruction: Clearing forests, draining wetlands, destroying coral reefs for farming, building, and development.
Pollution: Air, water, and land pollution harm organisms and ecosystems.
Climate Change: Changing temperatures and weather patterns are making it difficult for many species to survive.
Overexploitation: Overfishing, overhunting, and over-harvesting of plants and animals can drive species to extinction.
Invasive Species: Introducing non-native species to new environments can cause harm to native species.
Ways to Conserve Biodiversity (Protect it):
Protecting Habitats: Creating national parks, nature reserves, and protected areas to conserve natural environments.
Sustainable Use of Resources: Using resources in a way that meets our needs now without harming future generations. This includes sustainable fishing, forestry, and agriculture.
Reducing Pollution: Cleaning up pollution and preventing new pollution.
Combating Climate Change: Reducing greenhouse gas emissions to slow down climate change.
Captive Breeding Programs: Breeding endangered species in zoos and wildlife parks to increase their numbers and sometimes reintroduce them to the wild.
Seed Banks: Storing seeds of different plant species to conserve genetic diversity.
Raising Awareness: Educating people about the importance of biodiversity and how to protect it.
Chapter B7: Ideas about Science
1. Nature of Scientific Explanations
Science is Based on Evidence:
Evidence is Key: In science, explanations about how the world works are always based on evidence. Evidence is information that we collect through careful observations and experiments.
Not Just Guesswork: Scientific explanations are not just guesses or opinions. They are supported by facts and data that we can see, measure, and test.
Examples of Evidence:
Observations: Watching plants grow, noticing animal behaviors, seeing different types of cells under a microscope.
Measurements: Recording the temperature of water as it boils, measuring the height of plants, counting the number of insects in a garden.
Experimental Results: Data collected from experiments that test a specific idea (hypothesis). For example, an experiment to see if plants grow better in sunlight or shade.
Explanations May Change with New Evidence:
Science is Always Learning: Science is not a fixed set of facts. It's a way of learning and understanding, and our understanding can improve as we gather more information.
New Discoveries: Scientists are always making new discoveries and finding new evidence. New technology and research methods allow us to learn more about the world.
Refining Explanations: When new evidence is found, it might support our current explanations, or it might challenge them. If new evidence doesn't fit with an old explanation, scientists may need to change or refine the explanation to better fit all the evidence.
Example of Changing Explanations:
Early Ideas about the Earth: Long ago, people thought the Earth was flat. This was based on their everyday observations (the ground looks flat).
New Evidence (Round Earth): As people explored more, and with new evidence like observing ships disappearing hull first over the horizon, and eventually seeing pictures from space, the explanation changed to the Earth being a sphere (round). The new evidence provided a better explanation.
DNA Model: The understanding of DNA also changed over time. Scientists like Watson, Crick, Franklin, and Wilkins built upon each other's evidence to develop our current model of DNA's structure.
Science is a Process of Improvement: The fact that scientific explanations can change is not a weakness, but a strength of science. It means science is always trying to get closer to the truth by constantly testing and improving our understanding based on the best available evidence.
2. Scientific Enquiries
What is a Scientific Enquiry? A scientific enquiry is like an investigation to answer a question about the world around us. It's a process scientists use to explore and learn.
Devising and Carrying Out Enquiries: This involves several steps:
Asking a Scientific Question: Start with something you want to find out about the natural world. The question should be something that can be investigated scientifically, meaning you can collect evidence to answer it.
Examples of Questions: "Do plants grow taller in sunlight or shade?", "Does exercise make your heart beat faster?", "What types of insects are found in our schoolyard?".
Planning the Enquiry (Devising): Decide how you are going to investigate your question. This includes:
Choosing the Right Techniques: Think about the best way to collect evidence to answer your question. Will you do an experiment, make observations, survey people, or use secondary sources (like books or websites)?
Selecting Appropriate Equipment: Decide what tools and equipment you will need to collect your data. Examples: Rulers, thermometers, microscopes, timers, notebooks, cameras, identification guides.
Making Predictions (Hypothesis): Make an educated guess about what you think the answer to your question might be, based on what you already know. This is your hypothesis. Example: "I predict that plants will grow taller in sunlight than in shade."
Carrying Out the Enquiry (Carrying Out): Follow your plan and collect data (information). This might involve:
Performing Experiments: Setting up a fair test where you change one thing (variable) and measure the effect on something else, keeping everything else the same (controlled variables).
Making Observations: Watching and recording what you see, hear, smell, taste, or feel.
Taking Measurements: Using equipment to measure things accurately and recording your measurements.
Recording Data Carefully: Write down your observations and measurements in a clear and organized way (tables, charts, diagrams).
Collecting and Analysing Data: Once you have collected your data, you need to make sense of it.
Organizing Data: Put your data into tables, graphs, or charts to make it easier to see patterns and trends.
Analysing Data: Look at your data and try to identify any patterns or relationships. What does your data tell you? Do your results support your prediction (hypothesis)?
Drawing Conclusions: Based on your data analysis, decide what the answer to your original question is.
What does your evidence show? Summarize your findings.
Does it support your hypothesis? Explain whether your results agree with your prediction or not.
Explain your conclusion using your evidence. Use your data to support your conclusion.
Think about any problems or limitations in your enquiry and how you could improve it next time.
Example of a Scientific Enquiry:
Question: Does exercise make your heart beat faster?
Techniques and Equipment: Technique: Measuring pulse rate. Equipment: Stopwatch or timer, fingers to feel pulse.
Hypothesis: Exercise will make the heart beat faster.
Carry out enquiry: Measure pulse rate at rest, then after doing jumping jacks for 1 minute, then measure pulse rate again. Repeat several times and with different people.
Collect and Analyse Data: Record pulse rates in a table and calculate averages. Compare pulse rates before and after exercise.
Conclusion: Data shows pulse rate increased after exercise. Conclusion: Exercise makes the heart beat faster. This supports the hypothesis.
Key Skills in Scientific Enquiry:
Observation: Paying close attention to the world around you.
Questioning: Asking questions and being curious.
Planning: Thinking carefully about how to investigate a question.
Measuring and Recording: Collecting data accurately and systematically.
Analysing: Looking for patterns in data and making sense of it.
Drawing Conclusions: Using evidence to answer questions.
Evaluating: Thinking about the strengths and weaknesses of an investigation and how to improve it.
