Unit 3 STEM Test Study Guide

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Three energy roles

producer, consumer, decomposer

How is an organism's energy role determined?

how it obtains food and how it interacts with other organisms

Producer

an organism that can make its own food

Consumer

an organism that obtains energy by feeding on other organisms

Herbivores

Consumers that eat only plants

Examples of Herbivores

cow, rabbit, chicken

Carnivores

Consumers that eat only animals

Examples of Carnivores

wolves, walruses, snakes

Omnivores

Consumers that eat both plants and animals

Examples of Omnivores

bears, crows, humans

Scavenger

A carnivore that feeds on the bodies of dead organisms

Examples of Scavengers

catfish, vulture, hyena

Decomposers

organisms that break down biotic wastes and dead organisms and return raw materials to the environment

Examples of Decomposers

mushrooms, bacteria, mold

How does energy enter into most ecosystems?

as sunlight and converted into food by producers

How does energy move through an ecosystem?

when one organism eats another

Food Chain

A series of events in which one organism eats another and obtains energy

Food Web

many overlapping food chains in an ecosystem

Energy Pyramid

A diagram that shows the amount of energy that moves from one feeding level to another in a food web

What type of consumer can be both a first and second level consumer at the same time?

omnivores

How much energy is transferred to the next level in an energy pyramid?

about 10%

What is most of the food energy converted to in each level?

Heat

Where is the most food energy available?

Producer level

How do human activities affect ecosystems?

Human activities may affect the balance in an ecosystem and thereby change the ecosystem

Examples of human activities affecting ecosystems

overusing resources and using technology in agriculture

Ecosystem

An area where organisms interact with one another as well as with the nonliving parts of it.

How do populations change in size?

when new members join the population or when members leave the population.

Ecologists

scientists who study biotic and abiotic factors of an ecosystem and the interactions between them

Birth Rate

the number of births in a year per 1,000 individuals in a given time period

Death Rate

the number of deaths in a year per 1,000 individuals in a given time period

Population Statement

If birth rate > death rate, population size increases.

If death rate > birth rate, population size decreases.

If death rate > birth rate, population size decreases.

Immigration

moving into a population

Emigration

leaving a population

Population Density

The number of individuals in an area of a specific size

Population density equation

number of individuals/unit area

Two ways to join a population

birth and immigration

Two ways to leave a population

death and emigration

Limiting Factors

environmental factors that causes a population to stop growing or decrease in size

Examples of limiting factors

food, water, space, weather conditions

Carrying Capacity

The largest population that an area can support

Natural Selection

A process in which an organism gets a characteristic which makes it better suited to a specific environment and may eventually become common in that species.

Adaptations

the behaviors and physical characteristics that allow organisms to live successfully in their environments

Examples of adaptations

giraffe's neck, human's brain, elephant's trunk

Niche

the role of an organism in its habitat

What does a niche include?

what type of food the organism eats, how it obtains this food, what other organisms eat it, when and how the organism reproduces, and the physical conditions it requires to survive.

Three major types of interactions among organisms

competition, predation, symbiosis

competition

the struggle between organisms to survive as they attempt to use the same limited resources

examples of competition

Weeds competing with crops for sunlight, water, and food

Predation

An interaction in which one organism kills another for food or nutrients

Predator

The organism that does the killing in a predation interaction

Prey

The organism that is killed in a predation interaction

Symbiosis

Any relationship in which two species live closely together and at least one of the species benefits

Types of symbiosis

mutualism, commensalism, parasitism

Mutualism

A relationship between two species in which both species benefit

Examples of mutualism

bees and flowers, birds and crocodiles, oxpecker and impala

Commensalism

A relationship between two organisms in which one organism benefits and the other is unaffected

Examples of commensalism

whales and barnacles, remora fish and sharks, trees and birds

Parasitism

A relationship between two organisms of different species with one living inside or on the other where one benefits and the other is harmed

Parasite

An organism that benefits in a parasitism relationship; usually smaller than host

Host

An organism that is harmed in a parasitism relationship

Examples of parasitism

fleas and dogs, cowbird and yellow warbler, fish lice and fish

Interspecific Competition

competition between members of different species

Intraspecific Competition

competition between members of the same species

Hypothesis Format

If, then, because

Examples of Producers

corn, apple, banana