Chapter 21-1 and Chapter 22

Species InteractionsCommunity EcologyFood Webs

Predation

•Predator-captures, kills and consumes another individual

•Prey-is captured and consumed for food

Predators, Prey and Natural Selection

• A predator’s survival depends on its ability to capture food, but a prey’s survival depends on its ability to avoid being captured.

Mimicry• Deception is important in

antipredator defenses.• In a defense called mimicry, a

harmless species resembles a poisonous or distasteful species.

• The harmless mimic is protected because it is often mistaken to be its dangerous look-alike

MimicryMonarch

Viceroy

Plant-Herbivore Interactions

• Animals that eat plants are called herbivores.

• Through natural selection, plants have evolved adaptations that protect them from being eaten.

• Physical defenses, such as sharp thorns, spines, sticky hairs, and tough leaves, can make a plant more difficult to eat.

Plant-Herbivore Interactions

• Plants have also evolved a range of chemical defenses.

• They synthesize chemicals from products of their metabolism, called secondary compounds, that are poisonous, irritating, or bad tasting.

• Examples are the tobacco plant and poison ivy and poison oak.

• Many medicines are derived from secondary compounds.

Secondary Compounds

Purple Coneflower or Echincaea.

Immune system

Willow Tree

aspirin

stop

Parasitism

• Parasitism- a species interaction that resembles predation in that one individual is harmed while the other benefits

• Parasite- feeds on another individual, harming it

• Host-fed upon by another organism• Ectoparasites-external, ticks, fleas, lice• Endoparasites-internal, worms, protists

Ectoparasites

Endoparasites

Competition• Competition results from niche overlap.• Competition is the use of the same

limited resource by two or more species.

• Competitive exclusion is when one species is eliminated from a community due to competition.

• One species uses a resource more efficiently and has a reproductive advantage over the other.

• Competition is the most intense between similar species using the same resources.

Mutualism and Commensalism

• Mutualism- a cooperative relationship in which both partners benefit

• Some mutualistic relationships are so close that neither partner could live without the other.

• Pollination is a major mutualistic relationship that benefits the world.

Mutualism and Commensalism

• Commensalism- a relationship between organisms in which one organism benefits and one organism is unaffected.

• One example is birds eating insects and lizards that are flushed out by buffalo.

• The buffalo is not harmed and does not benefit but the birds clearly benefit from the buffalo.

Mutualism

CommensalismThese are mainly commensalism but could change to mutualism if the situation changes.

Essential Questions

• Explain how predators differ from parasites. Give an example of each kind of organism.

• Some harmless flies resemble bees and wasps. What is this mechanism called? Evaluate its importance as a defense mechanism.

• Describe two chemical defenses of plants.• What is symbiosis?• What are the 4 kinds of symbiosis?

StopMagic School Bus

Producers• Producer-makes its own food, autotroph• Chemosynthesis-produce carbohydrates

from inorganic molecules• Autotrophs, which include plants and

some kind of protists and bacteria, manufacture their own food.

• Because autotrophs capture energy and use it to make organic molecules, they are called producers.

Producers• Most producers are photosynthetic, so

they use solar energy to power the production of food.

• Some autotrophic bacteria do not use sunlight as an energy source.

• These bacteria carry out chemosynthesis, which means they produce carbohydrates by using energy from inorganic (non-living) molecules.

Consumers• Consumers-heterotrophs, must eat

other organisms to obtain energy• Herbivores-animals that eat

producers, plant eaters or bacteria eater

• Carnivores-animals that eat other consumers

• Omnivores-animals that eat both producers and consumers

Consumers

• Detritivore-consumers that feed on dead or dying organisms and waste products

• Decomposers-break down complex molecules in dead tissues and wastes into simpler molecules

What Am I?

zebra consumer

producer

decomposer

lion

grass

mushroom

deer

Energy Flow• Trophic level-the organisms’ position in the

sequence of energy transfers• Whenever one organism eats another,

molecules are metabolized and energy is transferred

• One way to follow the pattern of energy is to group organisms in an ecosystem based on how they obtain energy.

• Producers are always on the first trophic level.

• Herbivores are on the second level and carnivores on the third…etc.

Food Chains and Food Webs

• Food chain-single pathway of feeding relationships among organisms in an ecosystem that results in energy transfer

• Food web-interrelated food chains that connect together

• The bottom of energy diagrams is always the biggest.

• There are always more producers than consumers.

Essential Questions• Why are autotrophs essential

components of an ecosystem?• What role do decomposers play in an

ecosystem? Why is this role important?• How does a food chain differ from a

food web?• What would happen if you removed any

organism from a food web or chain? Be specific!

Commensalism

Mutualism

commensalism

Parasitism

Predation

Parasitism

mutualism

mutualism