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Y8 Ecosystems Knowledge Organiser

Lesson 1 Food Chains and Webs:

A food chain is a diagram that shows what an organism eats. It shows the transfer of energy between organisms.
Food chains have the following features:

The first organism is a producer – a green plant or algae that makes its own food by photosynthesis.
The second organism is a herbivore (it eats plants) and is called a primary consumer – this means it is the first organism to eat things.
The third organisms is a carnivore (it eats other animals) and called a secondary consumer.
Some food chains have a fourth organism (called a tertiary consumer) but they don’t usually have more than this.
Arrows show the transfer of energy (stored in food) from one organism to the next.

Lesson 2 Disruption to Food Chains and Webs:

Interdependence is the way in which living organisms depend on each other to survive, grow and reproduce. For example many fruits and vegetables rely on bees to pollinate their flowers so they can reproduce.
Organisms in a food web depend on each other for survival. They are interdependent.
The number of animals or plants of the same species that live in the same area is called a population. If the size of one population of a certain species changes, it will have an effect on the size of a population of a different species.
For example, if a rabbit’s predator is a fox, then if the rabbit population decreases, this may decrease the fox population, unless they have something else to eat. If the fox does have another prey to eat then their population might decrease because they are being eaten more.
Bioaccumulation is when toxins build up in a food chain. The animals at the top of the food chain are affected most severely. This is what happens:

Small amounts of toxic substances - often from human activity - are taken up by plants.
These plants are eaten by primary consumers.
The primary consumers are eaten by secondary consumers, and the secondary consumers are eaten by higher level consumers.
At each stage (trophic level) of the food chain, harmless substances are excreted but the toxins remain in the tissues of the organisms - so the concentration of toxin becomes most concentrated in the body tissues of the animals at the top of the food chain.

Lesson 3 Ecosystems:

An ecosystem is the name given to the plants and animals that are found in a particular location, and the area that they live in.
The organisms in an ecosystem are known as a community. The area they live in is called a habitat. The conditions found in a habitat are known as the environment.
Organisms that co-exist (live in the same ecosystem together) each have their own niche. A niche is a particular place or role that an organism has. For, they may live in a particular part of the ecosystem or they may have a particular food source.

In this food chain the acacia tree is the producer. The giraffe is a herbivore and it is the primary consumer. The lion is a carnivore and it is the secondary consumer. Giraffe can also be called prey because it gets eaten by the lion, which we call a predator.

Most animals eat more than one type of organism, so will be involved in more than one food chain. We can show this by linking food chains together to make a food web.

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Lesson 4 Competition:

Animals compete with each other for food, water, space and mates.
Plants compete with each other for light, water, space and minerals.
When a predator feeds on just one type of prey, there is a strong link (interdependence) between both populations. This can be shown on a graph.

When the prey population increases, the predator population also increases because they have more to eat.
As the predator population increases, more prey get eaten, so the prey population decreases.
Eventually there is not enough food for all the predators so their population decreases.
Then the prey population increases due to being eaten less, so the cycle starts again.

Lesson 5 Aerobic Respiration:

Your body needs energy to move, grow, keep warm, keep your heart beating and much more.
You get your energy from a sugar called glucose, which is in carbohydrates in your food. In your cells, glucose reacts with oxygen from the air you breathe in a process called aerobic respiration. This process transfers energy to your cells and makes the waste products carbon dioxide and water.
The word equation for aerobic respiration is:

glucose + oxygen → carbon dioxide + water

Glucose comes from broken down carbohydrates in your food. It is absorbed into the blood by the wall of the small intestine. It then travels to every cell in the blood plasma – the liquid part of your blood.
Oxygen diffuses into the bloodstream in the alveoli (air sacs) in your lungs. It is carried around your body by the red blood cells.
Carbon dioxide made during respiration diffuses out of your cells into the blood plasma. The blood transports it to the lungs, where it diffuses into the air sacs to be exhaled.

Lesson 6 Adaptations for Respiration:

Respiration happens inside tiny structures inside your cells called mitochondria.
Different cells have different numbers of mitochondria. For example, red blood cells have 0 mitochondria – they are pumped around the body by the heart. Muscle cells have 1900 mitochondria – they need lots of energy to contract to allow your body to move.
Mitochondrial disease is a disease where the mitochondria in a person’s cells are not releasing another energy.

Lesson 7 Anaerobic Respiration:

Anaerobic respiration is a type of respiration that does not use oxygen.
Your body uses anaerobic respiration to transfer energy from glucose when there is not enough oxygen for aerobic respiration to take place.
Anaerobic respiration happens during strenuous exercise like when you sprint, as the body needs extra energy to be released quickly. It only happens for short periods of time.
The word equation for anaerobic respiration is:

glucose → lactic acid

Anaerobic respiration transfers less energy than aerobic respiration and the lactic acid made can cause painful cramps in your muscles.
When you have finished exercising you keep on breathing heavily. The extra oxygen you inhale breaks down the lactic acid. The oxygen needed for this process is called the oxygen debt.
Other animals perform anaerobic respiration when they do vigorous exercise. Plants usually respire aerobically, but if they can’t get oxygen from the soil (like when they are surrounded by water) they respire anaerobically.

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Lesson 8 Biotechnology:

Biotechnology is the use of biological processes or organisms to create useful products such as food and drinks.
Yeast is a microorganism used in the production of bread and many alcoholic drinks.
Yeast performs a chemical reaction called fermentation. Fermentation is a type of anaerobic respiration.
The word equation for fermentation is:

glucose → ethanol + carbon dioxide

To make bread, flour, water and yeast are mixed to make dough. The dough is then left in a warm place to rise. The yeast respire by fermentation and turn the sugars in the flour into ethanol and carbon dioxide. The carbon dioxide gas is trapped as bubbles inside the dough, making it rise.
The dough is then baked in the oven and the ethanol evaporates. The bubbles of gas expand, making the bread rise further.
Alcoholic drinks are made by fermenting plant sugars. Wine is made when yeast is used to ferment grape sugar. Beer is made when yeast is used to ferment sugar in malted barley.

Lesson 9 Photosynthesis:

Plants make food through the process of photosynthesis.
Photosynthesis is a chemical reaction in which plants take in carbon dioxide and water and change them into glucose. Glucose is the plant’s food – just like us they use it for energy. Oxygen is also made and this is released back into the atmosphere.
Plants use light from the Sun as energy to perform photosynthesis.
The word equation for photosynthesis is:

carbon dioxide + water → glucose + oxygen

Photosynthesis mainly takes place in the chloroplasts in the leaf cells, but a small amount happens in the stem. Leaves and stems are green because they contain a green pigment called chlorophyll. Chlorophyll absorbs light from the Sun for photosynthesis.

Lesson 10 Leaves:

Leaves are adapted to perform photosynthesis. Most leaves:

are green – the contain chlorophyll which absorbs sunlight
are thin – they allow carbon dioxide and oxygen to diffuse in and out easily
have a large surface area – to absorb as much light as possible
have veins – these contain xylem tubes which transport water, and phloem tubes which transport glucose

Tiny holes found on the bottom surface of the leaf are called stomata (singular: stoma). Their function is allow carbon dioxide to diffuse in, and oxygen and water vapour to diffuse out. Stomata are open and closed by guard cells. They are open in the day and closed at night.

The leaf is divided into two main layers:

palisade layer – contains cells full of chloroplasts to perform photosynthesis
spongy layer – contains air spaces to allow gases to diffuse through the leaf

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Lesson 13 The Movement of Substances in Plants:

Plants have tubes adapted to transport water, minerals and sugars.
These tubes are called xylem and phloem.

Xylem transport water/minerals upwards.
Phloem transports sugar and amino acids in both directions

On the bottom surface of the leaf there are tiny holes called stomata. As well as letting carbon dioxide in and letting oxygen out, stomata also let water vapour out as it evaporates into the air. This loss of water vapour is called transpiration. Plants often need to close their stomata to stop the loss of water vapour.
As water evaporates from the leaves, more water is pulled up through the stem through the xylem to take its place. This is called the transpiration stream.

Lesson 12 Plant Minerals:

For healthy growth, plants need four minerals from the water in the soil:

nitrates for healthy growth
phosphates for healthy roots
potassium for healthy leaves and flowers
magnesium for making chlorophyll

If a plant does not get enough minerals its growth will be poor. This is called a mineral deficiency.

nitrate deficiency causes poor growth and older leaves are yellow
phosphorus deficiency causes poor root growth and younger leaves look purple
potassium deficiency causes yellow leaves with dead patches
magnesium deficiency causes yellow leaves

Farmers use fertilisers to add minerals to their soils. For example NPK fertiliser contains nitrogen (N), phosphorus (P) and potassium (K).

Lesson 11 Investigating Photosynthesis:

Plants turn the glucose made in photosynthesis into starch as an energy store. This starch can be tested for using iodine.
To test for starch first you kill leaf in boiling water. Then you place it in ethanol to remove the chlorophyll. Then you wash the leaf with water to remove the ethanol and soften the leaf. After this you add a few drops of iodine solution onto the leaf. If starch is present, the iodine will turn from yellow/brown to blue/black. This shows that the plant has been photosynthesizing.
You can measure the rate of photosynthesis by measuring the amount of oxygen a plant produces in a given time. You can do this by placing an upturned test-tube over some pondweed. You can then count the bubbles given off in a specific time period (like every minute), or you can time how long it takes to collect a specific volume of gas. The gas is oxygen.
You can use this experiment to test the effect of different variables on the rate of photosynthesis. For example, you could test the effect of light intensity by moving the pondweed different distances from a lamp.
Three main factors affect the rate of photosynthesis:

The higher the light intensity, the faster the rate of photosynthesis.
The greater the carbon dioxide concentration, the faster the rate of photosynthesis.
The higher the temperature, the faster the rate of photosynthesis.

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Example questions:

What do we call the first organism in a food chain?

What is a herbivore?

In what position would you find a secondary consumer in a food chain?

What is bioaccumulation?

What is a food web?

What do we called the way in which living organisms rely on each other to survive?

What is a niche?

What is a habitat?

What will happen to the numbers of a prey population if the predator population increases?

What is the word equation for aerobic respiration?

What carries oxygen around your body?

Where is glucose absorbed into the blood?

Where does respiration happen?

What is the word equation for anaerobic respiration?

Which type of respiration releases more energy?

What is the oxygen debt?

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Example questions:

What is the word equation for fermentation?

Which product of fermentation is used to make bread rise?

What is fermented to make alcoholic drinks?

What is the word equation for photosynthesis?

Where does photosynthesis happen?

What pigment is used to absorb light in plants?

Why do leaves have a high surface area?

What gas diffuses into a leaf through the stomata?

What is used to test for starch?

What is the first main step in the starch test?

What can you do to measure the rate of photosynthesis in pondweed?

Which plant mineral is used for making chlorophyll?

What plant minerals are in NPK fertiliser?

What is the role of the xylem?

What is the role of the phloem?

What is transpiration?