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Evolution

Change in a species over time.

Adaptation

A trait that helps an organism survive and reproduce.

Fitness

An organism's ability to survive and reproduce.

Species

A group of organisms that can reproduce and produce fertile offspring.

Allele Frequency

How often a certain allele appears in a population.

Charles Darwin

Scientist who proposed evolution by natural selection.

Natural Selection

Organisms with helpful traits survive and reproduce more.

Darwin's Theory of Evolution

Populations change over time because organisms with beneficial traits survive and reproduce.

Normal Distribution

Most organisms have average traits and fewer have extreme traits.

Stabilizing Selection

Average traits are favored and extreme traits are selected against.

Stabilizing Selection Example

Average-sized human babies survive best.

Directional Selection

One extreme trait is favored.

Directional Selection Example

Dark peppered moths survived better during pollution.

Disruptive Selection

Both extreme traits are favored over average traits.

Disruptive Selection Example

Birds with very small or very large beaks survive better.

Gene Flow

Movement of genes between populations through migration.

Genetic Drift

Random changes in allele frequencies in a population.

Bottleneck Effect

A disaster suddenly reduces population size and genetic diversity.

Founder Effect

A small group starts a new population with different allele frequencies.

Homologous Structures

Similar body structures with different functions that show common ancestry.

Homologous Structures Example

Human arm and whale flipper.

Analogous Structures

Different body structures with the same function.

Analogous Structures Example

Bird wings and insect wings.

Vestigial Organs

Body parts with little or no current function that were useful in ancestors.

Vestigial Organ Example

Human appendix.

Fossils

Preserved remains or traces of ancient organisms.

Fossils Evidence

Show how species changed over time.

Embryology

Study of embryos to compare development between species.

Embryology Evidence

Similar embryos suggest common ancestry.

DNA and Proteins Evidence

Species with similar DNA are closely related.

Divergent Evolution

Species become more different over time.

Divergent Evolution Example

Darwin's finches.

Convergent Evolution

Different species evolve similar traits.

Convergent Evolution Example

Sharks and dolphins.

Coevolution

Two species evolve in response to each other.

Coevolution Example

Bees and flowers.

Producer/Autotroph

Organism that makes its own food using sunlight or chemicals.

Producer Example

Plants.

Consumer/Heterotroph

Organism that gets energy by eating other organisms.

Herbivore

Consumer that eats only plants.

Herbivore Example

Rabbit.

Carnivore

Consumer that eats only animals.

Carnivore Example

Lion.

Omnivore

Consumer that eats both plants and animals.

Omnivore Example

Bear.

Decomposer

Organism that breaks down dead organisms and recycles nutrients.

Decomposer Example

Fungi and bacteria.

Biogeochemical Cycle

Movement of matter through living and nonliving parts of Earth.

Biosphere

All living things on Earth.

Geosphere

Land, rocks, and soil on Earth.

Atmosphere

Layer of gases surrounding Earth.

Hydrosphere

All water on Earth.

Photosynthesis Equation

6CO2 + 6H2O + light → C6H12O6 + 6O2

Photosynthesis Inputs

Carbon dioxide, water, and sunlight.

Photosynthesis Outputs

Glucose and oxygen.

Photosynthesis Purpose

Plants make food using sunlight.

Cellular Respiration Equation

C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP

Cellular Respiration Inputs

Glucose and oxygen.

Cellular Respiration Outputs

Carbon dioxide, water, and ATP energy.

Cellular Respiration Purpose

Cells release energy from food.

Aerobic Respiration

Respiration that requires oxygen and produces more ATP.

Anaerobic Respiration

Respiration that does not require oxygen and produces less ATP.

Fermentation

Process that releases energy without oxygen.

Energy Pyramid

Diagram showing how energy moves through trophic levels.

Energy Pyramid Facts

Producers have the most energy and only about 10% transfers to the next level.

Hydrologic Cycle

Movement of water through evaporation, condensation, precipitation, and runoff.

Nitrogen Cycle

Movement of nitrogen through air, soil, plants, animals, and bacteria.

Nitrogen-Fixing Bacteria

Bacteria that convert nitrogen gas into usable forms for plants.

Carbon Cycle

Movement of carbon through photosynthesis, respiration, decomposition, and fossil fuels.

Energy in Ecosystems

Energy flows one way and is eventually lost as heat.

Matter in Ecosystems

Matter is recycled through ecosystems.

Population

Group of the same species living in one area.

Habitat

Place where an organism lives.

Niche

An organism's role or job in an ecosystem.

Exponential Growth

Rapid population growth with unlimited resources.

Exponential Growth Graph

J-shaped curve.

Logistic Growth

Population growth that slows near carrying capacity.

Logistic Growth Graph

S-shaped curve.

Carrying Capacity

Largest population an environment can support.

Density-Independent Factors

Factors that affect populations regardless of size.

Density-Independent Examples

Floods, fires, droughts, hurricanes.

Density-Dependent Factors

Factors that affect larger populations more strongly.

Density-Dependent Examples

Disease, competition, predation.

Competition

Organisms fighting for the same resources.

Competition Example

Lions competing for food.

Predation

One organism hunts and eats another organism.

Predation Example

Hawk eating mouse.

Symbiosis

Close relationship between two different species.

Parasitism

One organism benefits while the other is harmed.

Parasitism Example

Tick on a dog.

Mutualism

Both organisms benefit.

Mutualism Example

Bee and flower.

Commensalism

One organism benefits while the other is unaffected.

Commensalism Example

Barnacles on a whale.

Human Dependence on Resources

Humans rely on water, food, fossil fuels, forests, and minerals.

Pollution

Contamination of air, water, or land.

Deforestation

Cutting down forests.

Habitat Destruction

Damage to ecosystems where organisms live.

Climate Change

Long-term changes in Earth's climate.

Global Warming

Increase in Earth's average temperature due to greenhouse gases.