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.

WHY?
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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.

How Come?
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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 algae 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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What is Photosynthesis?

• The process of photosynthesis is a chemical
  reaction.
• It is the most important
• chemical reaction on our planet.

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What is the Equation for the Chemical Reaction of
Photosynthesis?
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What is the equation for the chemical reaction of
photosynthesis?
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What is the equation for the chemical reaction of
photosynthesis?
Six molecules of carbon dioxide react with six
molecules of water to form 1 molecule of glucose
and six molecules of oxygen.
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Describe Photosynthesis

• The process of changing light energy to chemical
  energy
• Energy stored as sugar
• Occurs in plants and some algae
• Plants need light energy, CO2, and H2O
• Takes place in the chloroplasts, using
  chlorophyll, the green pigment in plants

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What happens during photosynthesis?

• Plants capture light energy and use that energy
  to make glucose
• Sunlight provides the energy needed by
  chlorophyll to change molecules of carbon dioxide
  and water into glucose
• Oxygen is also released in this reaction

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What happens during photosynthesis?

• Carbon dioxide enters the leaf through holes
  called stomata
• CO2 combines with the stored energy in the
  chloroplasts through a chemical reaction to make
  glucose
• The sugar is moved through tubes in the leaf to
  the roots, stems and fruits of the plants
• Some of the sugar is used right away by the plant
  for energy some is stored as starch and some is
  built into plant tissue

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Why is this important to us?

• We cannot make our own food (glucose, energy), we
  must get our food from plants.
• Plants are the first step in the food chain.

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Why is this important to us?

• The oxygen released during photosynthesis is
  necessary for all living things.

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Learn more about photosynthesis at

• http//www.ftexploring.com/me/photosyn1.html

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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 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, fungi and earthworms.

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Symbiotic Relationships

• Symbiosis a beneficial relationship between 2
  organisms that live together.
• 3 types of symbiosis
• Commensalism 1 organisms benefits, the other
  neither benefits or is harmed.
• Parasitism 1 organisms benefits the other is
  harmed.
• Mutualism both organisms benefit.

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Commensalism

• Commensalism occurs in a relationship where one
  animal benefits and the other is unaffected.
• The dorsal fin of the Remora is modified into a
  sucker. They attach to sharks during feeding and
  eat the scraps. The sharks do not try to eat the
  Remora.

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Parasitism

• A parasite is an organism that lives on or in the
  body of another organism (the host)
• from whose tissues it gets its nourishment, and
• to whom it does some damage

• Animals are parasitized by viruses, bacteria,
  fungi, protozoans, flatworms (tapeworms and
  flukes), nematodes, insects (fleas, lice), and
  arachnids (mites).
• Plants are parasitized by viruses, bacteria,
  fungi, nematodes, and a few other plants.

The flea is common on dogs and cats
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Mutualism

• The clownfish feeds the anemone by gathering
  nutrients and also leaving nutritional waste on
  the tentacles.

• The clownfish can come in contact with the
  stinging tentacles of the sea anemone and not be
  harmed by them.
• At the same time, it receives protection from its
  enemies.

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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.