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Food Chains and Food Webs


Food Chains and Food Webs Science Foundations Predator and Prey Relationships One important interaction in the ecosystem is between predators and their prey. – PowerPoint PPT presentation

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Title: Food Chains and Food Webs

Food Chains and Food Webs
  • Science Foundations

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.

  • 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.

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.

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

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.

  • 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.

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

What is the Equation for the Chemical Reaction of
What is the equation for the chemical reaction of
What is the equation for the chemical reaction of
Six molecules of carbon dioxide react with six
molecules of water to form 1 molecule of glucose
and six molecules of oxygen.
Describe Photosynthesis
  • The process of changing light energy to chemical
  • 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

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

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
  • 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

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.

Why is this important to us?
  • The oxygen released during photosynthesis is
    necessary for all living things.

Learn more about photosynthesis at
  • http//

  • 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

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

  • 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.

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
  • Mutualism both organisms benefit.

  • 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

  • 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
  • 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

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

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.

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

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