Energy Flow Through Energy Flow Through Our EcosystemOur Ecosystem

Science 10Science 10

The vast majority of life on Earth The vast majority of life on Earth depends on depends on sunlightsunlight as its source of as its source of energy. energy.

Of all the solar energy that reaches the Of all the solar energy that reaches the earth, some of it penetrates or passes earth, some of it penetrates or passes through the earth's atmosphere to the through the earth's atmosphere to the Earth's surface, but only a Earth's surface, but only a smallsmall quantity quantity is used to drive the process of is used to drive the process of photosynthesis. photosynthesis.

Look at the picture!Look at the picture! About how much of the energy that reaches the About how much of the energy that reaches the

earth is actually used in earth is actually used in photosynthesisphotosynthesis??

Albedo Effect:Albedo Effect: The actual amount of energy that The actual amount of energy that

reaches the surface of the Earth is reaches the surface of the Earth is affected by the affected by the albedoalbedo effect of clouds effect of clouds and dust particles in the atmosphere.and dust particles in the atmosphere.

AlbedoAlbedo is a measure of the amount of is a measure of the amount of light reflected from an object (written as a light reflected from an object (written as a decimal value) that shows the decimal value) that shows the percentage of percentage of lightlight reflectedreflected..

For example, clouds have an average For example, clouds have an average albedoalbedo about about .27.27 so about so about 27%27% of the sun’s energy is of the sun’s energy is normally reflected by clouds back to space. normally reflected by clouds back to space.

On a clear day, more light would be able to On a clear day, more light would be able to penetrate to the Earths surface and as a result penetrate to the Earths surface and as a result a greater amount of photosynthesis should a greater amount of photosynthesis should occur.occur.

PhotosynthesisPhotosynthesis

a biological process, uses the energy of a biological process, uses the energy of sunlight to manufacture sugar, which sunlight to manufacture sugar, which serves as the universal food for life.serves as the universal food for life.

Oxygen produced as a product of Oxygen produced as a product of photosynthesis is released into the photosynthesis is released into the environment.environment.

Chemical Formula for Chemical Formula for PhotosynthesisPhotosynthesis

6CO6CO22 ++ 6H 6H22O O ++ sunlight energy sunlight energy →→ C C66HH1212OO66 ++ 6O 6O22 Where:Where:

COCO22 represents carbon dioxide represents carbon dioxide

HH22OO represents water represents water

CC66HH1212OO66 represents the sugar molecules represents the sugar molecules (carbohydrate)(carbohydrate)OO22 represents oxygen represents oxygen

To release the energy stored in the To release the energy stored in the sugar, organisms carry out a metabolic sugar, organisms carry out a metabolic process known as process known as cellular respirationcellular respiration. .

CC66HH1212OO66 ++ 6O 6O22 →→ 6CO 6CO22 ++ 6H 6H22O O ++ energy energy

This equation is the This equation is the reversereverse of our of our photosynthesis equation!photosynthesis equation!

The energy released during The energy released during cellular cellular respirationrespiration is what allows organisms to is what allows organisms to carry on their life processes or carry on their life processes or metabolic metabolic processesprocesses such as movement, growth, such as movement, growth, and reproduction. and reproduction.

This process does transfer energy from This process does transfer energy from the food to the organism for carrying life the food to the organism for carrying life processes, but also releases heat which processes, but also releases heat which can not be used any further. can not be used any further.

HeatHeat energy is energy is lostlost on a continuous basis on a continuous basis from all living things. from all living things.

Feeding Relationships in Our Feeding Relationships in Our EcosystemEcosystem

Science 10Science 10

Food Chain or Trophic StructureFood Chain or Trophic Structure

A A food chainfood chain shows how each living thing gets shows how each living thing gets its food. Some animals eat plants and some its food. Some animals eat plants and some animals eat other animals. animals eat other animals.

Corn → Mouse → Snake → HawkCorn → Mouse → Snake → Hawk

Each link in this chain is food for the next link. Each link in this chain is food for the next link. A food chain A food chain usuallyusually starts with plant life and starts with plant life and ends with an animal.ends with an animal.

First Link in our Food ChainFirst Link in our Food Chain

11st st link is plants. link is plants. Plants are called Plants are called

producersproducers or or autotrophsautotrophs because because they are able to “trap” they are able to “trap” solar energy from the solar energy from the Sun to produce oxygen Sun to produce oxygen and food (sugar) from and food (sugar) from carbon dioxide and carbon dioxide and water.water.

What about organisms that can’t make their What about organisms that can’t make their own food?own food?

Animals cannot make their own food so Animals cannot make their own food so they must eat plants and/or other they must eat plants and/or other animals. They are called animals. They are called consumersconsumers or or heterotrophsheterotrophs. There are three groups of . There are three groups of consumers.consumers.

Heterotrophs or ConsumersHeterotrophs or Consumers1.1. Animals that eat Animals that eat ONLY PLANTSONLY PLANTS are called are called herbivoresherbivores (or (or

primaryprimary consumers). consumers).

2.2. Animals that eat Animals that eat OTHER ANIMALSOTHER ANIMALS are called are called carnivorescarnivores..

carnivores that eat herbivores are called carnivores that eat herbivores are called secondarysecondary consumersconsumers

carnivores that eat other carnivores are called carnivores that eat other carnivores are called tertiarytertiary consumersconsumers

3.3. Animals and people who eat Animals and people who eat BOTHBOTH animals and plants are animals and plants are called called omnivoresomnivores..

What comes next in the Food Chain?What comes next in the Food Chain?

Then there are Then there are decomposersdecomposers or or detritivores detritivores or or saprobessaprobes (bacteria and (bacteria and fungi) which feed on decaying matter. fungi) which feed on decaying matter.

These decomposers speed up the These decomposers speed up the decaying process that releases mineral decaying process that releases mineral salts back into the food chain for salts back into the food chain for absorption by plants as nutrients. absorption by plants as nutrients.

Why there are more herbivores than Why there are more herbivores than carnivores?carnivores?

In a food chain, energy is In a food chain, energy is passed from one link to passed from one link to another. another.

When a herbivore eats, only a When a herbivore eats, only a small part of the energy small part of the energy ((10%)10%) that it gets from the that it gets from the plant food becomes new body plant food becomes new body mass. mass.

The rest of the energy (The rest of the energy (90%)90%) is is lostlost as heat or used up by as heat or used up by the herbivore to carry out its the herbivore to carry out its life processes (e.g., life processes (e.g., movement, digestion, movement, digestion, reproduction). reproduction).

ThereforeTherefore, when a carnivore eats , when a carnivore eats another animal, only a another animal, only a portionportion of the of the energy from the animal food is energy from the animal food is stored in its tissues. stored in its tissues.

In other words, organisms along a In other words, organisms along a food chain pass on much food chain pass on much lessless energy (in the form of body mass) energy (in the form of body mass) than they receive.than they receive.

Because of the large amount of Because of the large amount of energy that is energy that is lostlost at each link ... at each link ... PYRAMID OF ENERGYPYRAMID OF ENERGY

The further along the food chain The further along the food chain you go, the you go, the lessless food (and food (and lessless energy) remains available. energy) remains available.

Note that as we go up, there are Note that as we go up, there are fewerfewer giraffes than trees & giraffes than trees & shrubs and even fewer lions than shrubs and even fewer lions than giraffes. giraffes.

In other words, a large mass of In other words, a large mass of living things at the living things at the basebase is is required to support a few at the required to support a few at the top. top.

Why do most food chains have no Why do most food chains have no more than four or five links?more than four or five links?

There cannot be too many links in a single food There cannot be too many links in a single food chain because the animals at the end of the chain because the animals at the end of the chain would not get enough food (or energy) to chain would not get enough food (or energy) to stay alive.stay alive.

Most animals are part of more than Most animals are part of more than oneone food food chain and eat more than one kind of food in chain and eat more than one kind of food in order to meet their food and energy order to meet their food and energy requirements. requirements.

These These inter-connectedinter-connected food chains form a food chains form a food food webweb..

Food WebFood Web

Australian Grassland Food WebAustralian Grassland Food Web

Antarctic Food Web

Marine Food Web

African Grassland Food Web