Science Exam Week Notes #1

The information is from the Notes on Knowt.

Explain Photosynthesis in a sentence

Photosynthesis is how plants use sunlight, water and carbon dioxide to make their own food and give out oxygen

What are reactants and products of Photosynthesis?

Carbon Dioxide ( from the air ) Water ( from the soil ) Sunlight ( energy source ) - Glucose ( type of sugar ) Oxygen ( released into the air ).

What are adaptations of leaves for Photosynthesis? ( 6 )

Large surface area - to absorb as much sunlight as possible

Thin shape - so gases like carbon dioxide can move in and out quickly

Chloroplasts and chlorophyll - to trap sunlight energy

Veins ( including xylem and phloem ) - to carry water to the leaf and food away from it

Stomata - tiny holes underneath to let carbon dioxide in and oxygen out

Guard Cells - control the openings and closings of the stomata

What is Stomata?

Stomata are tiny holes on the underside of leaves that open and close to let gases move in and out. They allow carbon dioxide to enter for photosynthesis and let oxygen and water vapour out

How and why do plants make carbohydrates and water?

Plants make carbohydrates (like sugars) in their leaves using photosynthesis, and they get water and mineral nutrients from the soil through their roots to help them grow and stay healthy

Where does Aerobic Respiration happen? What is the formula/equation?

Happens in most plants and animals - Glucose + oxygen → carbon dioxide + water + energy

Where does Anaerobic Respiration happen? What is the formula/equation?

It happens when there is not enough oxygen ( like during a tough exercise ) -

• In animals: Glucose → lactic acid + a little energy

• In some microorganisms (like yeast): Glucose → alcohol + carbon dioxide + a little energy

What are Ecosystem Processes?

Ecosystem processes are the natural cycles and interactions that keep an ecosystem healthy and working properly.

What are the key processes in the Ecosystem Process? ( 5 )

Key processes include:

1. Photosynthesis – Plants use sunlight to make food and release oxygen.

2. Respiration – All living things break down food to get energy.

3. Decomposition – Dead plants and animals are broken down by decomposers (like bacteria and fungi), returning nutrients to the soil.

4. Nutrient cycling – Nutrients like nitrogen and carbon move through the soil, plants, animals, and air in a cycle.

5. Feeding relationships – How energy moves through food chains and food webs (producers → consumers → decomposers).

What is a simple summary of the Ecosystem Process?

Ecosystem Processes are the ways that nutrients and energy move through living things and the environment to keep everything alive and balanced.

What is electricity and what does it power?

Electricity is the flow of electrons through a wire and it powers things such as light TVs and Phones

What is a circuit?

Circuits are paths that electricity flows through - a circuit needs a power source ( like a battery), wires and components ( like bulbs ).

What are conductors and insulators?

Conductors ( like metals ) let electricity flow easily

Insulators ( like plastics ) don’t let electricity flow

What is magnetism?

Magnetism is a force caused by magnets, they have north and south poles like pole.

What do north and south poles attract?

Like poles repel, opposite poles attract.

What are magnetic materials?

Iron, cobalt, and nickel

What are magnetic fields?

They are invisible areas around the magnet where the force works.

What are electromagnets? How is it useful?

They are magnets made using electricity - useful in things such as electric bells and motors.

Why is electricity and magnetism connected?

Electricity is energy that flows in a circuit, and magnetism is a force from magnets. They're linked because electricity can make magnets and magnets can make electricity.

What are body systems?

A group of organs working together to preform a function.

Key body systems linked to energy and matter ( 5 )

1. Digestive system – Breaks down food into nutrients (like glucose) that our body can use.

2. Respiratory system – Brings oxygen into the body and gets rid of carbon dioxide.

3. Circulatory system – Moves oxygen, nutrients, and waste around the body in the blood.

4. Muscular system – Uses energy from food to help us move.

5. Excretory system – Removes waste from the body.

What are energy, matters and waste mater in body systems?

• Matter (food, oxygen, water) enters the body and is used in different systems.

• Energy is released from food during respiration (mainly in cells) to power everything we do—like moving, thinking, and growing.

• Waste matter (like carbon dioxide and urine) leaves the body to keep us healthy.

• The balance between energy intake and energy expenditure is critical for maintaining overall health and function.

• Nutrients from food play diverse roles; for example, carbohydrates are a primary energy source, while proteins are essential for growth and repair.

Important chemical processes in living things ( 6 )

1. Digestion – Breaks down food into small molecules (like sugars, amino acids, and fats) that the body can use for energy and growth.

2. Respiration – Releases energy from glucose (a type of sugar) in cells.

3. Photosynthesis – (In plants) uses sunlight to make food from carbon dioxide and water.

4. Protein synthesis – Cells make proteins using amino acids; proteins are needed for growth and repair.

5. Excretion – Removes waste chemicals (like urea and carbon dioxide) made during other chemical processes.

6. Enzyme activity – Enzymes speed up chemical reactions in the body, like breaking down food or copying DNA.

What is aerobic resperation?

Aerobic respiration is the process where cells use oxygen to break down glucose and produce energy, carbon dioxide, and water

When does Anaerobic respiration in humans occur?

It happens when thee isn’t enough oxygen for aerobic respiration

What is the process/equation of Anaerobic respiration in humans?

Glucose is broken down into lactic acid and a small amount of energy.

Glucose → Lactic acid + Energy (small amount)

Why is anaerobic respiration important?

Provides quick energy but produces lactic acid, which can cause muscle fatigue and soreness

Anaerobic respiration in microorganisms:

• Some microorganisms (like yeast) use anaerobic respiration for energy, and they undergo fermentation.

• Fermentation in yeast produces ethanol (alcohol) and carbon dioxide, along with a small amount of energy.

• Equation (in yeast):
  Glucose → Ethanol + Carbon dioxide + Energy (small amount)

Word summary for anaerobic respiration?

Anaerobic respiration is the process of breaking down glucose without oxygen to produce energy, often resulting in lactic acid in humans or alcohol and carbon dioxide in yeast

Anaerobic and aerobic reactants?

• Aerobic Respiration:

  • Reactants: Glucose + Oxygen

  • Occurs in: Most organisms, including humans (when enough oxygen is available).

• Anaerobic Respiration:

  • Reactants: Glucose (no oxygen involved)

  • Occurs in: Humans (during intense exercise) and some microorganisms (like yeast).

Anaerobic and aerobic products formed?

• Aerobic Respiration:

  • Products: Carbon dioxide + Water + Energy (lots of ATP)

  • Efficient: Produces a large amount of energy because oxygen is used.

• Anaerobic Respiration:

  • Products in Humans: Lactic acid + Energy (small amount of ATP)

  • Products in Yeast (Fermentation): Ethanol + Carbon dioxide + Energy (small amount of ATP)

  • Less efficient: Produces less energy and can result in by-products (like lactic acid or alcohol) that can be harmful in excess

Why is Anaerobic or Aerobic respiration good?

• Aerobic Respiration:

  • Efficient Energy Production: Provides a large amount of energy, which is good for long-term activity and growth.

  • Byproducts: Carbon dioxide and water, which are easy for the body to manage and remove.

• Anaerobic Respiration:

  • Quick Energy, but Less Efficient: Provides energy quickly when oxygen is not available, but it's only temporary.

  • Byproducts: In humans, lactic acid builds up, leading to muscle fatigue and soreness. In yeast, ethanol (alcohol) and carbon dioxide are produced, which can be useful in fermentation (e.g., brewing and baking).

Summary of difference for Anaerobic and aerobic respiration :

Oxygen required?

Energy produced?

By products?

Efficiency?

Yes for Aerobic, no, for Anaerobic

Much more in Aerobic

Aerobic produces carbon dioxide and water; anaerobic produces lactic acid or ethanol and carbon dioxide.

Aerobic is much more efficient

What are ecosystems made up of?

What do organisms in ecosystems depend on ( Food chain and Webs )

• Ecosystems are made up of living organisms (like plants, animals, and microbes) and non-living factors (like water, soil, and sunlight).

• Organisms in an ecosystem depend on each other for food, shelter, and survival. These relationships are part of food webs.

  • Food chains show how energy is passed from one organism to another (e.g., plants → herbivores → carnivores).

  • Food webs are more complex and show how different food chains overlap and connect in an ecosystem.

What do most plants need to do reproduce?

Many plants need to be pollinated to reproduce.

What are insect pollinators and why are they important?

• Insect pollinators (like bees, butterflies, and beetles) transfer pollen from one flower to another, helping plants produce seeds and fruit.

  • Pollination is critical for many food crops, like apples, strawberries, tomatoes, and almonds.

Importance of pollination?

• Pollination is essential for the production of many crops that humans rely on for food.

• Without pollinators, global food supply would be at risk because:

  • Many crops wouldn’t produce fruit or seeds.

  • Fewer crops would be available, leading to a lack of food and potentially higher prices.

• Insects (especially bees) are the most effective and important pollinators. They play a major role in maintaining food security by ensuring that crops can grow and reproduce.

How do organisms affect the environment?

• Habitat Changes: Organisms can change their environment to suit their needs. For example, beavers build dams that change the flow of rivers.

• Energy Flow: Organisms help move energy through ecosystems. Producers (plants) convert sunlight into energy through photosynthesis, which is passed on to herbivores, then carnivores.

• Waste and Decomposition: When organisms die, decomposers (like bacteria and fungi) break down their bodies, recycling nutrients back into the environment.

How are organisms affected by the environment?

• Availability of Resources: Organisms depend on their environment for resources like water, food, and shelter. Changes in the environment (like climate change or deforestation) can reduce these resources.

• Toxic Materials: Pollution (like chemicals, plastic, and heavy metals) can accumulate in the environment and harm organisms. For example:

  • Toxic materials can be absorbed by plants, which are then eaten by herbivores, and the chemicals move up the food chain.

  • Bioaccumulation is when toxins build up in the tissues of living organisms over time, which can be harmful to health.

What is the carbon cycle?

The carbon cycle is the process by which carbon moves through the atmosphere, living organisms, oceans, and Earth’s surface. Carbon is a key element that is involved in all living organisms and is essential for life.

Steps in the carbon cycle

Steps in the Carbon Cycle:

1. Carbon in the Atmosphere:
   Carbon exists in the air as carbon dioxide (CO₂). Plants absorb carbon dioxide from the atmosphere during photosynthesis to make their food.

2. Photosynthesis by Plants:
   Plants use sunlight, water, and carbon dioxide to produce glucose (a type of sugar) and oxygen. The carbon from CO₂ is stored in the plant as glucose.

3. Consumption by Animals:
   Animals eat plants (or other animals that ate plants), and the carbon in the plants moves into their bodies. The carbon is then used for energy, growth, and reproduction.

4. Respiration:
   Both plants and animals release carbon back into the atmosphere as carbon dioxide through respiration. This happens when they break down glucose for energy.

5. Decomposition:
   When plants and animals die, decomposers (like bacteria and fungi) break down their bodies. This releases carbon back into the soil and atmosphere as carbon dioxide.

6. Fossil Fuels:
   Over millions of years, some carbon gets trapped in fossil fuels (like coal, oil, and natural gas) when plants and animals are buried under layers of Earth. When humans burn fossil fuels for energy, carbon is released into the atmosphere.

7. Ocean Uptake:
   The oceans absorb large amounts of carbon dioxide from the atmosphere. Some of this carbon is used by marine plants, and some is stored in the deep ocean.

Why is the Carbon Cycle Important?

It is important for regulating carbon levels in the environment and supporting life on Earth.

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