Food Chains and Food Webs

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Food Chains and Food Webs

• Science Foundations

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Predator and Prey Relationships

• One important interaction in the ecosystem is
• between predators and their prey.
• Predators are organisms which hunt and feed
• on other organisms Whereas the living things
• that are eaten are referred to as prey.
• 1. To maintain balance in the ecosystem, the
  interaction between predator and prey should
  not be disturbed.

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Example

• In parts of the South, one natural predator of
• the white-tailed deer, the mountain lion, has
• been reduced in number. Because there are
• fewer mountain lions to prey on the deer, the
• deer population in some regions has risen
• tremendously.

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Food Chain

• A food chain is the relationship of organisms
• that depend on each other for energy or food.
• It is a straight line relationship such as algae
• is food for fish which are food for squid which
• are food for sharks.

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Food Web

• A food web is more complex and is a food
• chain with the interrelated chain of organisms
• that depend on each other for food.
• If one organism is removed, other organisms
• may be endangered or possibly die out.

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Food Web
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Carrying Capacity

• Carrying capacity is the number of individuals
• in a population that the resources can support.
• This provides for a balanced ecosystem.

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Trophic Levels

• The living things in an ecosystem can be
• divided into four levels. Each step in a food
• chain or food web is called a trophic level.
• Producers are the first step.
• Consumers are the next steps.
• Each step depends on the step below it for
• food and to provide its energy.

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Producers

• Producers are the green plants and some
• bacteria and alga that are able to make their
• own food from water, the sun, carbon dioxide
• in the air, and minerals in the soil.
• When plants make their own food, they use
  sunlight. This process is called photosynthesis.

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Consumers

• Consumers are the animals that rely on other
• organisms for food. This group can be further
• divided into three groups
• Primary consumers are herbivores, or plant
  eaters. Examples some insects, deer, or mice.
• Secondary consumers are carnivores, or flesh
  eaters. They feed on herbivores. Examples
  snakes and coyotes
• Tertiary consumers can be carnivores or
  omnivores, which eat both plants and animals.
  Example hawks and humans

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Scavengers

• Scavengers feed on dead organisms. They
• include earthworms, ants and vultures.

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Decomposers

• Decomposers are organisms that break down
• dead organic matter. This decomposition
• produces many of the raw materials that are
• used by the producers in photosynthesis.
• Examples are bacteria and fungi.

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Ecological Pyramids

• Ecological pyramids are diagrams that show
• each trophic level in a biome. There are three
• types
• Energy pyramid
• Biomass pyramid
• Numbers pyramid

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Energy Pyramid

• The energy pyramid shows the transfer of
• energy from one level to the next. The bottom
• of the food chain shows the largest amount of
• energy which comes from the sun then as you
• move up energy is used but also lost in the
• form of heat energy.

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Energy Pyramid
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Biomass Pyramid

• The biomass pyramid is based on the
• mass of organic material at each level.

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Numbers Pyramid

• The Numbers pyramid shows the relative
• numbers of organic material at each level.