Food ConnectionsSNC 1DR.H. King Academy

What is the origin of all animals’ food?

PLANTS! Whether herbivore or

carnivore, all of our food comes from plants.

Photosynthesis Plant leaves contain chlorophyll in the

chloroplast organelle. Plants use chlorophyll to capture the energy in sunlight and convert it into chemical energy. They then use this chemical energy for all the processes in their cells.

This process is called photosynthesis. The equation for photosynthesis is:

Carbon dioxide gas + water + sunlight glucose + oxygen gas

Photosynthesis

Photosynthesis Glucose is a simple form of sugar. All

sugars are carbohydrates, and carbohydrates contain energy. Therefore, carbohydrates are stored energy.

Oxygen gas is what we breathe in. The air we breathe is 21% oxygen, and almost all of it was produced by photosynthesis. This includes plants on land and in the ocean.

Cellular Respiration Cellular Respiration is the process of using energy

to keep our bodies functioning. Both plants and animals need a continuous supply

of energy for growth, repair of tissues, and reproduction.

The process plants and animals use to obtain energy from glucose is called cellular respiration. In cellular respiration, glucose combines chemically with oxygen from the air, in what looks like almost the reverse of photosynthesis. The equation is:

Glucose + oxygen gas Carbon dioxide gas + water + energy

Photosynthesis vs. Cellular Respiration Do plants perform photosynthesis?

Do animals perform photosynthesis?

Do plants perform cellular respiration?

Do animals performs cellular respiration?

Therefore, plants can make their own food (photosynthesis) and use it (cellular respiration). Animals cannot make their own food, but they do use food. How do animals get their food?

Photosynthesis and Cellular Respiration

What is the relationship between photosynthesis and cellular respiration?

Trophic Levels In a food chain,

food moves through trophic levels

Producers are plants. They are ALWAYS at the first trophic level, located at the bottom.

Trophic Levels Producers are plants. They make their own

food through photosynthesis Primary consumers are herbivores. They

eat plants. Give an example. Secondary consumers are carnivores. They

eat primary consumers. Give an example. Tertiary consumers are carnivores. They

eat secondary consumers. Give an example. A carnivore that has no predators is called a

“top carnivore”. Give an example.

Omnivores Omnivores eat both plants and animals. For

example, a bear. So what is its trophic level? Well let’s look at what it eats: When the bear is eats berries, it is a primary consumer. When the bear is eats rabbits, it is a secondary

consumer. When the bear is eats salmon, it is a tertiary consumer

However, if you have to choose one trophic level for the sake of simplicity, you must state the bear’s highest trophic level: “tertiary consumer”.

A bear is also a “top carnivore” because it has no predators (unless you consider humans!)

Detritivores and Scavengers Detritivores eat organic matter (dead organisms and

their waste). Scavengers are a type of carnivore that does not hunt

animals. Instead, it eats the leftovers of dead or dying animals.

Which of the species below is a detritivore? Which is a scanveger?

Decomposers Decomposers play an essential role in food chains. Decomposers break down organic matter. They

take nutrients from the organic matter and release them back into the ecosystem.

Fungi and many bacteria are decomposers. Instead of consuming food, they release chemicals called enzymes into the organic matter. These enzymes break down the organic matter and release nutrients. The decomposers can then absorb the nutrients.

Detritivores are classified as decomposers, but not all decomposers are classified as detritrvores since many fungi and bacteria cannot directly eat organic matter.

Decomposers This fungus is feeding on the organic matter

in the soil. As it does, nutrients in the organic matter are released into the soil.

Decomposers play a vital role in ecosystems. They help put nutrients back into the ecosystem so that they can be recycled by producers.

Without decomposers, nutrient cycles would be incomplete.

Food Chain Food chains show the feeding relationship

between trophic levels. It starts with producers and ends with the last consumer.

Identify the trophic levels in the food chain below

Food Web Ecosystems have several species that often

eat more than one type of food and have more than one predator.

For example, the fox’s prey is the squirrel, the hare, and the grouse. Its predator is the lynx. The lynx’s prey is the fox, and also the squirrel and the hare. The relationships are complex and intertwined.

Therefore a food web is used to illustrate these complex relationships.

Food Chain vs. Food Web A food web is actually several food

chains woven together Look at the food web in the last slide.

Identify the multiple food chains starting with the white spruce as the producer.

Energy and Trophic Levels When a consumer eats another organism,

does it absorb all of its energy? Example: If a caterpillar eats 100 J of leaves,

does it retain all of the 100 J? If yes, if a bird eats the caterpillar, does it then

retain all the 100 J from the leaves? The answer to both is no. In fact, the caterpillar would only retain 10 J of

the leaves. And if the bird ate the caterpillar, it would only retain 1 J of the energy from the leaves.

What happens to energy? When one organism consumes another

organism, here is what happens to the energy: 60% of the energy cannot be used and is

passed through waste 30% of the energy is used to for cellular

respiration (keeps the body running) 10% of the energy is used to make new body

tissues Therefore, only 10% of the energy is

retained in its body.

What happens to energy This caterpillar ate 100 J of the

leaf. However, only 10 J got stored as body tissue.

Therefore, when a bird eats the caterpillar, the bird will only get 1 J of energy that came from the leaf.

When a fox eats the bird, the fox will only get 0.1J of energy that originally came from the leaf.

Energy and Trophic Levels Therefore, the caterpillars need to eat a

lot of leaves to get enough energy in its body…. And then the birds would need to eat a lot of caterpillars to get enough energy in its body….. And then the foxes would need to eat a lot of birds to get enough energy in its body.

Energy Pyramid Energy pyramids

show the amount of available energy at each trophic level

The more trophic levels that exist in a food chain, the less energy there is left from the original amount at the bottom.

Energy Pyramid Only 10% of energy can be passed up to the next

trophic level Therefore, in food chains, there has to be more

producers than primary consumers, more primary consumers than secondary consumers, and more secondary consumers than tertiary consumers.

As you move up the food chain, there are fewer and fewer organisms. This is why it’s called a food pyramid, because it gets smaller and smaller at the top.

Energy Consumption Which consumes more energy? An herbivore or

a carnivore? A carnivore.

When an herbivore consumes 1000 J of plants, that’s all in consumes.

However, when a carnivore that consumes 1000 J of prey, the prey had to consume 10000 J of plants. So the carnivore indirectly consumes 10x more energy!

Given this knowledge, can you explain what would happen if the number of secondary and tertiary consumers increased in an ecosystem? (e.g. if the number of foxes and lynx increased).

Niches Ecosystems are kept balanced so that there aren’t

too many primary consumers, and in turn fewer secondary consumers, and then even fewer tertiary consumers

To keep a balanced ecosystem, every species has its niche: food, predator, habitat, etc.

Niches reduce competition between species for the same territory and resources.

Top carnivores play an important role. For example, the lynx. If the lynx were to be extirpated in an ecosystem, there would be too many hares. If there are too many hares, they would eat too many plants, not leaving enough food for the rest of the ecosystem. The lynx’s presence ensures there is enough food for lower trophic levels.

What about humans? Who consumes more food energy? A

human omnivore, or a human vegetarian? The omnivore. Vegetarians consume less

energy and have a lower ecological footprint compared to non-vegetarian humans. Vegetarians only eat plants. Omnivores also eat animals, and these animals eat large quantities of plants (or other animals) in order to grow.

Think of it this way. The grain could feed one meat-eater; or it could feed 10 vegetarians.

Homework Read pp. 28-32 Answer Questions:

p. 29 #1-4 p. 35 #1-3, 9, 12-16