Biology Summer Homework C1-C12
Chapter 1: Characteristics and Classification of Living Organisms
Biology is the study of organism which is a complete living thing
Living organisms share a 7 set of essential characteristics that distinguish them from non-living things. These include:
Movement – Ability to change position or place.
Respiration – Release of energy from food (usually glucose).
Sensitivity – Ability to detect and respond to stimuli.
Growth – Permanent increase in size and drymass.
Reproduction – making more organism of the same kind
Excretion – Removal of waste products.
Nutrition – Taking in and using nutrients for energy and growth.
This is often remembered by the acronym MRS GREN.
The Binomial System
A common ancestor is an organism from the past that two or more different species evolved from.
Organisms are grouped together based on shared features or genetic similarities.
A species is defined as a group of organisms that can reproduce to produce fertile offspring.
Using the binomial system where the scientific name of an organism is made up of two parts starting with the genus (always given a capital letter) and followed by the species (starting with a lower case letter) and always in italics (which indicates they are Latin) e.g. Homo sapiens
The classification is: Kingdom, Phylum, Class, Order, Family, Genus, Species
Dichotomous Keys
Dichotomous means ‘branching into two’ and it leads the user through to the name of the organism by giving two descriptions at a time and asking them to choose. Each choice leads onto another two descriptions. Until it successfully navigate the answer
Types of Kingdoms
Organisms are classified into five kingdoms:
Animals
*Multicellular
*their cells contain a nucleus but no cell walls or chloroplasts
*heterotrophic.
Plants
*multicellular
*have cell walls (cellulose)
*perform photosynthesis.
Fungi
*mostly multicellular
*do not photosynthesize but feed by saprophytic
*made of chitin cell walls.
Protoctists
*most are unicellular but some are multicellular
have a nucleus, but only some have cell walls and chloroplasts
consist of a diverse features
Prokaryotes
*mostly unicellular
*have cell walls and cytoplasm but no nucleus or mitochondria
*DNA floats freely in the cytoplasm
The Animal Kingdom
Vertebrates
Vertebrates are animals that have backbones. These are the most familiar animals – fish, amphibians, reptiles, birds and mammals.
Invertebrates
Arthropods are animals with jointed legs, but no backbone. They are a very successful group, because they have a waterproof exoskeleton.
The Plant Kingdom
Plants are green, due to the presence of the green pigment chlorophyll.
The plant kingdom includes organisms such as ferns and flowering plants
Ferns
Have leaves called fronds
Do not produce flowers but it reproduce by spores
Flowering plants
Reproduce sexually by means of flowers and seeds
Divided into two groups – monocotyledons and dicotyledons
MONOCOT VS DICOT
Practice Questions with Answers
Q1: List three characteristics shared by all living organisms.
Ans: Movement, Nutrition, and Growth.
Q2: Why do scientists classify organisms?
Ans: To identify and organize the group for easier study and to understand their relationships.
Q3: Compare features of animals and fungi.
Ans: Animals are multicellular, they don’t have cell walls, and they are heterotrophs ; fungi are also heterotrophic but feed on dead or decaying material and have chitin cell walls.
Exam Question and Answers
Which characteristic is not shown by all living organisms?
A. Excretion
B. Movement
C. Photosynthesis
D. Respiration
Answer: C. Photosynthesis
Explanation:
All living things share the characteristics of MRS GREN.
Photosynthesis is not one of these universal characteristics. However plants, algae, and some bacteria can photosynthesise to make food.
Chapter 2: Organisation of the Organism
Living organisms are made of cells, the basic units of life.
Animal Cell
contain a nucleus and distinct membrane
do not have cell walls and chloroplasts
contain carbohydrates stored as glycogen
Plant Cell
contain a nucleus with a distinct membrane
cell walls made out of cellulose
contain chloroplasts to perform photosynthesis
carbohydrates stored as starch or sucrose
Function of parts of cells
Structure | Function |
|---|---|
Nucleus |
|
Cytoplasm |
|
Cell membrane |
|
Ribosomes |
|
Vacuole |
|
Chloroplast |
|
Cell wall |
|
Mitochondria |
|
Bacterial Cell
Bacteria are tiny, single-celled organisms with various shapes and sizes.
consist of cell wall (made of peptidoglycan) cell membrane, cytoplasm, and ribosomes
do not have a nucleus
Some bacteria have plasmids – small loops of extra DNA carrying additional genes.
They lack membrane-bound organelles, like mitochondria and chloroplasts.
Some bacteria have flagella – tail-like structures used for movement.
Specialized Cells
Specialized cells are cells that have adapted specific features to carry out particular jobs in the body.
Cells become specialized through a process called differentiation.
Cells
The smallest working units in a living organism; they carry out essential life processes.
Tissue
Groups of similar cells that work together to do a particular job.
Organs
Structures made up of different types of tissues that carry out specific tasks.Organ Systems
Sets of organs that work together to perform important functions in the body.
Ciliated Cell
Function: Moves mucus in the trachea and bronchi
Neuron
Function: Sends electrical signals (nerve impulses
Red Blood Cell
Function: Carries oxygen
Sperm Cell
Function: Reproduction (fertilizes the egg)
Egg Cell
Function: Reproduction
Root Hair Cell
Function: Absorption of water and mineral ions
Palisade Mesophyl Cell
Function: perform photosynthesis
Sizes of Specimen
The formula for calculation of Magnification is:
Magnification = Image size ÷ Actual size
Always millimeters as unit
Tip: Use IAM triangle diagram
Practice Questions with Answers
Q1: Define a tissue and give two examples.
Ans: tissue is made up of a group of cells that work together to perform a certain function. Example: xylem and phloem
Q2: What is the role of an organ system?
Ans: An organ system is a group of organs working together to perform a specific function. They play an important role in carrying out the major functions of our body such as breaking down foods, coordination and responses etc.
Q3: How do specialised cells contribute to the function of an organism?
Ans: Specialized cells perform different tasks efficiently, helping the organism to function properly.
Connections to Bigger Concepts
Links to cell structure and its function (Chapter 1).
Differentiating the different level of organisation
Helps understand how damage tissues or organs affects the organism.
Exam Question and Answers
Question:
a) i. One way to tell these are plant cells and not animal cells:
ii. One way to tell these are not bacterial cells:
iii. One structure missing in these cells that you would expect in a palisade cell:
b )i. Function of the nucleus :
ii. Function of ribosomes :
Answer:
a) i. They have a cell wall
ii. They have a nucleus
iii. Chloroplast
b) i. It contains the cell’s genetic material and controls the cell’s activities.
Ii. This is the main site of protein synthesis where amino acids are assembled into protein and follow the instructions of DNA.
Chapter 3: Movement into and out of cell
Diffusion
Diffusion is the movement of molecules from a region of its higher concentration to a region of its lower concentration
The energy for diffusion comes from the kinetic energy of this random movement of molecules and ions
Passive process (no energy needed)
Osmosis
The diffusion of water molecules through a partially permeable membrane from a region of higher water potential to a region of lower water potential.
The cell membrane is partially permeable which means it allows small molecules to pass through but not larger molecules
Osmosis in Plants:
Pure water → water enters → turgid
Concentrated solution → water leaves → flaccid / plasmolysis
Osmosis in Animals:
Pure water → water enters → may burst
Concentrated solution → water leaves → cell shrinks
Active Transport
The movement of substances from low to high concentration using energy from respiration.
This process is carried out by carrier proteins in the cell membrane.
Practice Questions with Answers
Q1: Compare diffusion and active transport.
Ans: Diffusion moves substances from a high concentration to low concentration without using energy while active transport moves substances from a low concentration to high concentration using energy.
Q2: What happens to a plant cell in pure water?
Ans: Water enters by osmosis so the vacuole swells, then it becomes turgid.
Q3: Give an example of osmosis in animals.
Ans: Water moving into red blood cells.
Practical Reflection
Potato osmosis experiment in different salt solutions.
In higher salt concentrations, the water will lose which the cell will shrink. While the potato in a solution with a lower salt concentration, it will gain water and swell. On the other hand, The potato in a solution with the same salt concentration will not change in size.
Connections to Bigger Concepts
It can be link to homeostasis
Water uptake for the roots in Chapter 8
Exam Question and Answers
1. Where does the energy for diffusion come from?
A glucose
B kinetic energy of molecules and ions
C respiration in mitochondria
D sunlight answer with explanation
Answer: B. kinetic energy of molecules and ions
Explanation:
Diffusion is passive and happens because particles naturally move using their own kinetic energy.
Chapter 4: Biological molecules
Carbohydrates (Starch)
Monomer: Monosaccharide
Elements: C, H, O (1:2:1 ratio)
Function: Main energy source
Test: Iodine → blue-black
Carbohydrates (Reducing Sugar)
Monomer: Monosaccharide
Elements: C, H, O
Function: Quick energy source
Test: Benedict’s (heat) → brick-red/orange
Lipids (Fats & Oils)
Monomers: Glycerol + 3 fatty acids
Elements: C, H, O
Function: Long-term energy storage, insulation, protection
Test: ethanol emulsion test → milky white
Proteins
Monomer: Amino acids
Elements: C, H, O, N (sometimes S)
Function: Growth, repair, enzymes, hormones, antibodies
Test: Biuret Solution → purple/lilac
DNA
Monomer: Nucleotide (sugar + phosphate + base)
Elements: C, H, O, N, P
Function: Stores genetic information
The bases always pair up
Adenine always pairs with Thymine (A-T)
Cytosine always pairs with Guanine (C-G)
DCIPIP Test
Purpose: To test for the presence of vitamin C.
Practice Questions with Answers
Q1: Explain the role of proteins in the body
A: Proteins build tissues and speed up reactions. They also fight infections.
Q2: Why are vitamins important?
A: They are needed for boosting our immune system, for forming tissues, and supporting cells to do their jobs.
Q3: Describe the test for starch.
A: We use iodine solution and wait for it to turn blue-back to indicate the presence of starch.
Practical Reflection
Iodine turned potato blue-black (starch), Benedict’s solution made glucose solutions turn orange-red when heated, Biuret solution turned purple with protein, and ethanol emulsion test turned milky appearance with lipids.
Exam Question and Answers
1. Glucose, starch, glycogen and cellulose are carbohydrates.
a. Which of these substances are found in plants only, and not in animals?
b. List the elements that the molecules of all these substances contain.
c. Describe the structure of a starch molecule
d. Glucose is a reducing sugar. Describe how you could test a liquid to find out if it contains glucose
a. starch and cellulose
Explanation: Starch store energy and cellulose cell walls are made up of cellulose which occur only in plants.
b. Carbon, Hydrogen, Oxygen
Explanation: All carbohydrates are made from these three elements in a ratio of about 1:2:1.
c. A starch molecule is made of many glucose that is joined into a long chain.
d. 1. Add Benedict’s solution to the liquid sample.
2. Heat the mixture
3. Wait until it turns brick-red or orange to show glucose is present.
Chapter 5: Enzymes
Enzymes are biological catalysts made of proteins that speed up chemica reactions without being used up
Each enzyme has an active site with a specific shape.
Only a substrate with a complementary shape can bind to the active site (like a key fitting a lock).
When bound, an enzyme-substrate complex forms, lowering the activation energy needed for the reaction.
The products are released, and the enzyme is free to catalyse another reaction.
Examples of Enzymes
Amylase – Breaks starch into maltose (in saliva and pancreas).
Maltase – Breaks maltose into glucose (in small intestine).
Protease – Breaks proteins into amino acids (stomach, pancreas).
Lipase – Breaks lipids into fatty acids and glycerol (pancreas).
Factors Affecting Enzyme Activity
Temperature
As temperature increases, enzyme activity increases (more kinetic energy → more collisions).
At the optimum temperature activity is highest.
Above this, enzymes denature: bonds break, active site changes shape, substrate no longer fits.
pH
Each enzyme has an optimum pH where it works best.
Extreme pH changes disrupt bonds, altering the active site → denaturation.
Example: Pepsin works best in acidic conditions (pH ~2), amylase in neutral (pH ~7).
Practice Questions with Answers
Q1: What happens to enzyme activity above its optimum temperature?
Ans: Enzymes will denature after its optimum temperature, which means the enzymes will decrease the speed sharply.
Q2: Define Enzyme Specificity?
Ans: Each enzyme binds only to its specific substrate (like a lock and key) due to the unique shape of its active site.
Q3: .Explain Enzyme denaturation
Ans: At high temperature or exceeding its optimum temperature the enzymes will slows down and affects its active site’s shape hence losing its function.
Practical Reflection
Investigating the catalase in potatoes by adding it to hydrogen peroxide at different temperatures. At warm temperatures, oxygen bubbles formed quickly. In boiling water, there were no bubbles. The enzyme had been destroyed by heat.
Exam Question and Answers
A solution containing an enzyme and no other substance was tested.
Which test would give a positive result?
A Benedict’s test
B biuret test
C ethanol test
D iodine test
Ans: B
Chapter 6: Plant Nutrition
Plants are autotrophic organisms.
They make their own food through photosynthesis.
This process takes place in the chloroplasts of plant cells, mainly in the leaves.
Chlorophyll, the green pigment in chloroplasts, absorbs light energy from the sun.
This light energy is then converted into chemical energy, which is used to combine carbon dioxide and water to produce glucose and release oxygen.
Word equation:
Carbon dioxide + Water → Glucose + Oxygen
(light energy, chlorophyll)
How a Plant Uses Carbohydrates:
* Respiration – to release energy.
* Storing – converted to starch for later use.
* Making sucrose – for transport to other parts of the plant.
* Making cellulose – to build and strengthen cell walls.
* Making proteins – combine with nitrates to form amino acids.
* Making lipids – stored in seeds.
* Making nectar – to attract pollinators.
* Making other substances – e.g., chlorophyll.
Plants also require mineral nutrients from the soil for healthy growth:
Nitrate ions – needed to make amino acids, proteins, and nucleic acids. A deficiency results in poor growth and yellow leaves.
Magnesium ions – needed to make chlorophyll. A deficiency causes chlorosis, where leaves turn yellow and photosynthesis slows.
The rate of photosynthesis can be affected by limiting factors:
Light intensity – more light increases photosynthesis until another factor becomes limiting.
Carbon dioxide concentration – more CO₂ increases the rate until light or temperature becomes limiting.
Temperature – increases the rate until the optimum temperature is reached; above this, enzyme denaturation slows the process.
Leaf Structure
Cuticle – Protective, waterproof layer on top of the leaf to prevent water loss.
Upper epidermis – Thin, transparent layer letting light pass to the palisade cells beneath.
Palisade mesophyll – Column-shaped cells packed with chloroplasts for light absorption and photosynthesis. This is where photosynthesis occur the most.
Spongy mesophyll – Loosely packed cells with air spaces to allow efficient gas exchange.
Lower epidermis – Contains stomata and guard cells.
Guard cells – Control opening and closing of stomata to regulate gas exchange and water loss.
Stomata – opening pores for gas exchange;
Vascular bundle – Vein structure containing xylem and phloem for transport.
Xylem – Moves water to leaf cells for photosynthesis and replaces water lost by transpiration.
Phloem – Moves sucrose and amino acids to other parts of the plant.
Practice Questions
Write the word equation for photosynthesis
Carbon dioxide + Water → Glucose + Oxygen
Why are nitrates important for plants?
Nitrates are essential for making amino acids and chlorophyll.
What causes chlorosis?
Magnesium deficiency and Nitrate Deficiency
Practical Reflection
The leaf was boiled to soften it, placed in ethanol to remove chlorophyll, rinsed in water, and iodine was added. A blue-black color appeared where starch was present, showing photosynthesis had occurred.
Connections to Bigger Concepts
Links to Chapter 4 because glucose produced can be stored as starch or used to make proteins and lipids.
Connects to Chapter 8 (Transport in Plants) since water and minerals are transported to leaves for photosynthesis.
Exam Question and Answers
A student investigated the necessity of light for photosynthesis. He covered a leaf with black paper to prevent light reaching it. What is an appropriate control for his experiment?
A a leaf that has been destarched
B a leaf that is not covered with black paper
C a leaf that is partly white and partly green
D a leaf that has no carbon dioxide provided
Answer: B- a leaf that is not covered with black paper
Explanation: The control leaf should be the same as the test leaf but still get light. In order to see if photosynthesis will occur since black paper absorbs the light.
Chapter 7: Human Nutrition
Human nutrition is the process by which the body takes in and uses food for energy, growth, and repair.
Key nutrients and their functions:
Carbohydrates – Energy source.
Proteins – Growth and repair.
Lipids – Energy storage and insulation.
Vitamins & minerals – Various roles such as boosting immune system
Fibre – Aids movement of food in the gut.
Water – For transport and chemical reactions.
Digestive System
The human digestive system is a long tube called the alimentary canal, supported by accessory organs. Its job is to break down food into small, soluble molecules that the body can absorb and use.
Ingestion – Taking in food and drink into the mouth.
Digestion – Breaking down large, insoluble molecules into small, soluble molecules:
Mechanical digestion – Physical breakdown of food (chewing, churning in stomach).
Chemical digestion – Enzymes break down food molecules (e.g., amylase breaks starch into maltose).
Absorption – Movement of small, soluble molecules from the gut into the blood or lymph (mainly in the small intestine).
Assimilation – Using absorbed molecules in cells for energy, growth, and repair.
Egestion – Removal of undigested food as faeces.
Organs of the Digestive System
Mouth – Mechanical digestion by teeth; saliva contains amylase to start starch digestion; saliva also moistens food to form a bolus.
Oesophagus – Transports food to the stomach by peristalsis (wave-like muscular contractions).
Stomach – Muscular walls churn food; secretes gastric juice containing pepsin and hydrochloric acid (kills bacteria and creates acidic pH for enzymes).
Small intestine – The main site of digestion and absorption:
Duodenum – Receives bile (emulsifies fats) from the liver and gall bladder, and digestive enzymes from the pancreas.
Ileum – Has many villi and microvilli to increase surface area for absorption.
Large intestine – Absorbs water and salts; remaining waste forms faeces.
Rectum and anus – Stores and then ejects faeces.
Accessory Organs
Liver – Produces bile to emulsify fats; stores glycogen; processes absorbed nutrients.
Gall bladder – Stores bile before releasing it into the duodenum.
Pancreas – Produces enzymes (amylase, protease, lipase) and secretes them into the small intestine; also makes sodium hydrogen carbonate to neutralise stomach acid.
Adaptations for Absorption in the Small Intestine
Villi and microvilli provide a large surface area.
Thin epithelium reduces diffusion distance.
Rich blood supply maintains a steep concentration gradient.
Lacteals absorb fats into the lymphatic system.
Teeth
Types of teeth in humans:
Incisors – Chisel-shaped; used for cutting and biting food.
Canines – Pointed; used for tearing food.
Premolars – Broad surface with ridges; used for chewing and grinding food.
Molars – Larger, broad-surfaced; used for chewing and crushing food.
Structure of a tooth:
Enamel – Hard, outer covering; the hardest substance in the body; protects the tooth from damage.
Dentine – Bone-like layer under the enamel; supports the enamel.
Pulp cavity – Contains blood vessels and nerves that supply the tooth.
Cement – Covers the root; helps anchor the tooth in the jaw.
Practice Questions with Answers
Q1: What is a balanced diet?
A diet containing all essential nutrients in correct proportions for health.
Q2: Name two deficiency diseases and their causes
Scurvy – Vitamin C deficiency leading to weak immunity and bleeding gums
Rickets – soft bones in children which means lack of Vitamin D
Q3: Why is fiber important?
Fibre can prevent constipation and regulates blood sugar.
Practical Reflection
Testing food samples for starch, sugar, protein, and fat using iodine, Benedict’s solution, Biuret reagent, and ethanol. This helped us understand the different nutrients contained in the food and their importance in a balanced diet.
Connections to Bigger Concepts
Links to Chapter 4 because the nutrients we eat are made of biological molecules like carbohydrates, proteins, and lipids.
Connects to Chapter 9 (Transport in Animals) since absorbed nutrients are transported in the blood to cells.
Exam Question and Answers
a.
G large intestine (colon)
J Liver
b.
A Salivary Gland
D Pancreas
c.
F Duodenum
d.
Churns food using mechanical digestion
Mixes food with gastric juice
Pepsin digests proteins into peptides
Produces hydrochloric acid to kill bacteria
Acid provides optimum acidic pH for pepsin
Turns food into small pieces into the small intestine
Chapter 8: Transport in Plants
Xylem & Phloem
Plants have two main transport vessels:
Xylem – carries water and minerals from the roots up to the stem and leaves.
Phloem – carries food (mainly sucrose and amino acids) from photosynthesising leaves to other parts of the plant.
These vessels are grouped together in vascular bundles found in the roots, stem, and leaves.
Adaptations of xylem vessels
Long continuous tubes formed by cells joined end to end without cross walls
Dead and hollow cells for easy water flow
Thick lignin walls for strength and supports
Root Hair Cells
Root hairs are single-celled extensions of epidermis cells in the root
They absorb water and minerals
Water enters root hair cells by osmosis
Osmosis occurs because soil water has higher water potential than the root hair cell’s cytoplasm
Root hair increases the surface area of the cells which means it can increase the amount of absorption of water and mineral ions.
Transpiration & Transpiration Pull
Transpiration is the process where water vapor is lost from plant leaves.
Process:
Water moves up the xylem from roots to leaves to replace water lost by transpiration
Transpiration involves water evaporating from mesophyll cell surfaces and diffusing out through stomata
Xylem cells have lignin in their walls, causing them to die and form hollow tubes joined end-to-end
Lignin strengthens the plant and helps it resist pressure from water movement
Water in the xylem flows in one direction only—from roots to leaves
Transpiration transports mineral ions throughout the plant
It provides water to keep cells firm and support the plant’s structure
Water from transpiration is essential for photosynthesis in leaf cells
Transpiration cools leaves by using heat energy to evaporate water, lowering leaf temperature
Water molecules stick together through cohesion, forming a continuous water column in the plant
Water travels up the xylem vessels in a steady transpiration stream from roots to leaves through the stem
Transpiration creates a tension or ‘pull’ on water in the xylem by the leaves
When transpiration rate increases, water is pulled up the xylem vessels faster
Translocation
sucrose and amino acids move in the phloem
Phloem is made of living cells with sieve plates for easy flow
Translocation moves sugars from source to sink (storage or use)
Transport direction changes with plant growth and season
Winter: storage organs → other parts for respiration
Spring: storage organs → growing areas
Summer: leaves → roots for storage as starch
*In summer leaves are source while roots are sink.
*In winter leaves are sink while roots source.
Practice Questions with Answers
What is transported by the phloem?
Phloem carries sugars and amino acids from leaves to other parts of plants
Describe Transpiration
Plants lose water as vapor through stomata that pulls water upward from roots.
How do root hairs aid water absorption?
a. it has large surface area that massively increase the root’s contact with soil water. and thin cell walls which allow easy osmosis.
Practical Reflection
Using a potometer to measure the rate of water uptake by a plant shoot. By changing light intensity, we saw that more light made the plant lose water faster, showing the link between transpiration and environmental factors.
Connections to bigger concept
Links to Chapter 6 because water and minerals are needed for photosynthesis.
Exam Question and Answers
What is a function of phloem but not xylem?
A supporting the plant
B transporting amino acids
C transporting mineral ions
D transporting water
Answer: B
Explanation: Phloem transports sucrose and amino acids, while xylem transports water and mineral ions.
Chapter 9: Transport in Animals
The circulatory system is an organ system, the role of which is to transport blood around the body.
Single circulation – Blood passes through the heart once per complete circuit (e.g., fish: heart → gills → body → heart).
Double circulation – Blood passes through the heart twice per complete circuit (e.g., humans: heart → lungs → heart → body → heart). This allows higher pressure to the body and lower pressure to the lungs.
The heart
Heart: A muscular organ with four chambers (two atria and two ventricles) that pumps blood.
Right side – receives deoxygenated blood from the body and pumps it to the lungs.
Left side – receives oxygenated blood from the lungs and pumps it to the body.
Veins carry blood to the heart; arteries carry blood away from the heart.
The septum is a muscular wall separating the two sides of the heart.
The heart is made of muscle tissue and is supplied with blood by the coronary arteries.
Ventricles have thicker walls than atria because they pump blood out of the heart and must generate higher pressure.
Left ventricle wall is thicker than the right because it pumps blood at high pressure to the whole body, while the right only pumps to the lungs at lower pressure.
The septum separates the two sides of the heart, preventing oxygenated and deoxygenated blood from mixing.
Valves stop blood from flowing backwards.
Atrioventricular (AV) valves separate atria from ventricles:
Tricuspid valve – right side
Bicuspid valve – left side
Open when atria contract, close when ventricles contract to prevent backflow into atria.
Semilunar valves are in the arteries leaving the heart (pulmonary artery and aorta)
Open when ventricles contract, close to stop blood returning to the heart.
Deoxygenated blood from the body enters the right atrium via the vena cava.
When the right atrium contracts, blood passes through the tricuspid valve into the right ventricle.
The right ventricle contracts, sending blood through the semilunar valve into the pulmonary artery.
Blood travels to the lungs, where it moves through capillaries around alveoli for gas exchange. Low pressure here prevents damage to the delicate capillaries.
Oxygenated blood returns to the left atrium via the pulmonary vein.
It passes through the bicuspid valve into the left ventricle.
The thick-walled left ventricle contracts forcefully, pumping blood into the aorta and around the body.
The semilunar valve in the aorta stops blood flowing back into the heart.
Coronary Heart Disease
A condition where the coronary arteries, which supply blood to the heart muscle, become narrowed or blocked.
Prevention:
Eat a balanced, low-fat diet
Exercise regularly
Avoid smoking
Manage stress
Maintain a healthy weight
Blood Vessels
Arteries
Carry blood away from the heart.
Thick muscular and elastic walls to withstand high pressure.
Small lumen (narrow opening).
No valves (except semilunar valves in the aorta and pulmonary artery).
Pulse can be felt.
Usually carry oxygenated blood (except pulmonary artery).
Veins
Carry blood towards the heart.
Thin walls with less muscle and elastic tissue (low pressure).
Large lumen for easier blood flow.
Contain valves to prevent backflow.
No pulse.
Usually carry deoxygenated blood (except pulmonary vein).
Capillaries
Tiny vessels linking arteries and veins.
Walls only one cell thick for short diffusion distance.
Narrow lumen to fit blood cells in single file for efficient exchange.
Allow exchange of gases, nutrients, and wastes between blood and tissues.
Components of Blood
Blood consists of red blood cells, white blood cells, platelets and plasma
Practice Questions with Answers
1. What is double circulation?
A system that passes to the heart twice which include Pulmonary and systemic circulation.
2. Function of red blood cells (RBCs)?
It carries oxygen and remove wastes
3. How do capillaries support exchange?
A wall one cell thick leading to a short diffusion distance for easier diffusion.
Large surface area for larger gas exchange.
Practical Reflection
This experiment investigated how exercise affects pulse rate. The resting pulse was recorded (72 bpm), then measured again after 2 minutes of exercise (108 bpm). The increase occurred because active muscles require more oxygen, forcing the heart to pump faster. This demonstrates the circulatory system's ability to meet the body's changing demands.
Connections to bigger concepts
Links to respiration (Chapter 11) (oxygen delivery for energy release).
Connects to human nutrition (Chapter 7) (blood transports digested nutrients).
Exam Question and Answers
D. Soluble fibrinogen is converted to insoluble fibrin.
Explanation:
During blood clotting, Fibrinogen is converted into fibrin by the enzyme.
Chapter 10: Diseases and Immunity
Pathogens
Pathogens
Disease-causing microorganisms
Cause transmissible diseases (passed between hosts)
Transmission Methods
Direct Contact:
Transfer of body fluids (blood, semen)
Examples: HIV, gonorrhoea, hepatitis B & C
Indirect Contact:
Contaminated surfaces/food/water
Airborne droplets/aerosols (e.g., flu, tuberculosis)
Vectors: Organisms like mosquitoes (malaria, dengue)
Active Immunity
Production of antibodies and memory cells by the immune system in response to a pathogen.
Provides long-lasting protection.
How It Develops
Natural Infection:
Pathogen enters the body → lymphocytes produce specific antibodies.
Memory cells remain for future faster response.
Vaccination:
Vaccine contains weakened/dead pathogen or its antigens.
Stimulates antibody production without causing disease.
Memory cells provide long-term immunity.
Antigens
Definition: Proteins/molecules on cell membranes (unique to each individual).
Function: Act as "markers" for cell identification.
Pathogen Recognition
Lymphocytes detect foreign antigens
Each antibody is specific to one antigen (lock-and-key model).
Antibody Production
Process:
Lymphocytes produce antibodies complementary in shape to pathogen antigens.
Antibodies bind to antigens, marking pathogens for destruction.
Result:
Pathogens are neutralized/destroyed
Memory cells retain antibody "blueprint" for future infections.
Immunity
• Slow response while lymphocytes produce specific antibodies
• Often causes illness during this initial period
• Creates memory cells that remember the pathogen
• Memory cells trigger rapid, stronger antibody production
• Usually prevents illness
• Mutating pathogens change their surface antigens
• Existing memory cells can't recognize the new antigens
• Requires fresh immune response why some diseases can be caught repeatedly
Vaccination
• Protects against specific diseases without exposure to dangerous pathogens
• Reduces risk of illness/death by stimulating immunity artificially
• Contains dead/altered pathogen with antigens (non-infectious)
• Triggers immune response:
Lymphocytes produce complementary antibodies
Memory cells are created for long-term immunity
• Effectiveness depends on vaccination rates (herd immunity)
Passive Immunity
• Fast-acting but short-term defense against pathogens using antibodies from another individual.
Active Immunity Vs. Passive Immunity
• Active immunity involves the body making its own antibodies
• Passive immunity provides immediate but temporary protection.
Practice Questions
How do vaccines work?
Vaccines contain dead pathogens
When injected, they stimulate white blood cells (lymphocytes) to produce antibodies.
Memory cells are created, providing long-term immunity.
If the real pathogen later infects the body, memory cells trigger rapid antibody production, preventing illness.
2. Name two physical barriers against infection.
skin and mucus
3. What causes antibiotic resistance?
Misuse of medications can worsen the symptoms
Not finishing the complete treatment of medications may also affect our immune system.
Practical Reflections
• Cause: Vibrio cholerae bacteria (transmitted via contaminated water).
• Prevention:
• Access to clean water and sanitation.
• Oral rehydration therapy (ORT) for treatment.
• Vaccination in high-risk areas.
Exam Question and Answers
What is the correct term for a microorganism that causes
disease?
A antibody
B host
C pathogen
D vector
Answer: C. Pathogen
Explanation: Pathogen is a microorganism that causes disease.
Chapter 11: Gas Exchange and Respiration
Large Surface Area
Increases the space available for diffusion
Faster diffusion due to more contact area for gases.
2. Thin Walls
One cell thick (short diffusion distance).
Reduces distance for gases to diffuse, speeding up the process.
3. Good Ventilation
Constant breathing refreshes air in alveoli
4. Rich Blood Supply
Capillaries surround alveoli/gills; xylem/ phloem in leaves.
Breathing Mechanism
Inhalation: Diaphragm contracts (flattens), ribs rise → volume 1, pressure v → air rushes in.
Exhalation: Diaphragm relaxes (domes), ribs fall → volume v, pressure 1 → air forced out.
Practice Questions
1. Gas Exchange in Alveoli
Oxygen diffuses from alveoli into blood capillaries while carbon dioxide moves in the opposite direction, enabled by the alveoli's thin walls, large surface area, and rich blood supply that maintain concentration gradients.
2. Aerobic Respiration Equation
C6 H12 O6 + 6O2 → 6CO2 + 6H2O + energy (ATP)
3. Aerobic vs. Anaerobic Respiration
Aerobic respiration uses oxygen to produce more ATP, while anaerobic respiration works without oxygen to make less ATP.
Exam Question and Answers
What are the products of anaerobic respiration in human muscle cells?
A carbon dioxide only
B carbon dioxide and water
C lactic acid only
D lactic acid and water
Answer: C- lactic acid only
Types of Respiration
Aerobic Respiration (with oxygen):
Occurs in mitochondria.
Produces 38 ATP per glucose molecule.
Waste products: CO2 + water.
Glucose + Oxygen → Carbon dioxide + Water + Energy (ATP)
Anaerobic Respiration (without oxygen):
Occurs in cytoplasm.
Produces only 2 ATP per glucose molecule.
In humans: Lactic acid
In yeast: Ethanol + CO2
Animals
Glucose → Lactic Acid + Energy (2 ATP)
Yeast
Glucose → Ethanol + Carbon dioxide + Energy (2 ATP)
Chapter 12: Coordination and Response
The Nervous System
Uses electrical impulses transmitted through nerve cells (neurons)
Enables rapid responses to stimuli
Components:
Central Nervous System (CNS): Brain and spinal cord
Peripheral Nervous System: Nerves throughout body
Features:
Impulses travel at high speed
Responses are short-lived and localized
The Endocrine System
Uses chemical messengers called hormones
Produced by endocrine glands
Enables slower, longer-term responses
Features:
Hormones travel via bloodstream
Effects are widespread and longer-lasting
Key Processes in the Nervous System
Reflex Actions
Automatic, rapid protective responses
Follow reflex arc pathway:
Stimulus → Receptor → Sensory Neuron → Relay Neuron (in CNS) → Motor Neuron → Effector → ResponseExamples: Knee jerk, blinking, withdrawal from pain
Synaptic Transmission
How neurons communicate at synapses
Process:
Electrical impulse reaches synapse
Triggers neurotransmitter release
Chemicals diffuse across synaptic cleft
Bind to receptors on next neuron
New electrical impulse generated
The Eye
Pupil Reflex
Bright light: Circular iris muscles contract → pupil constricts.
Dim light: Radial iris muscles contract → pupil dilates.
Hormonal Control (Endocrine System)
Major Glands and Hormones:
Pancreas: Insulin and glucagon (blood sugar regulation)
Adrenal: Adrenaline (fight or flight response)
Thyroid: Thyroxine (metabolism regulation)
Homeostasis Examples:
Blood Glucose Control:
Insulin lowers blood sugar
Glucagon raises blood sugar
Diabetes results from insulin deficiency
Thermoregulation:
Skin, sweat glands, and blood vessels regulate temperature
Cold: Vasoconstriction, shivering
Hot: Vasodilation, sweating
Plant Responses (Tropisms)
Phototropism: Growth towards light
Gravitropism: Response to gravity
Practice Question
Q: What is a reflex action?
A: An automatic, rapid response to danger
Q: Name a hormone and its role.
A: Insulin – Lowers blood glucose by converting it to glycogen in the liver.
Q: How do nerves transmit signals?
A:
Electrical impulse travels along neuron.
Chemicals (neurotransmitters) cross synapses to next neuron.
Exam Question and Answers
What is the response of a shoot to gravity?
A negative gravitropism
B negative phototropism
C positive gravitropism
D positive phototropism
Answer: B negative phototropism
because the shoot grows towards the gravity so its a negative photopism.