Bio Final Spring 26’

Vestigial organ

Body part with little/no current function, left from ancestors. Examples include human appendix, tailbone, whale pelvis, and snake leg bones.

Homologous structures

Structures that share the same origin but have different functions, indicating a common ancestor. Examples include human arm, bat wing, and whale flipper.

Analogous structures

Different structures that have the same function, like bird wings and insect wings.

Evidence for evolution

Includes fossils, DNA similarities, embryology, homologous structures, biogeography, and observations of natural selection.

Mechanisms of evolution

Five mechanisms are mutation, gene flow (migration), genetic drift, natural selection, and non-random mating.

Speciation

Occurs when populations become isolated and change over time until they can no longer reproduce together.

Types of natural selection

Includes directional (favors one extreme), stabilizing (favors average traits), and disruptive (favors both extremes). Example: peppered moths becoming darker (directional); human birth weight (stabilizing); small and large beaks surviving (disruptive).

Natural selection

The process by which organisms with helpful traits survive and reproduce more, resulting in those traits becoming more common over time.

Biological fitness

The ability to survive and reproduce successfully.

Steps of natural selection

1. Variation exists 2. Overproduction of offspring 3. Competition 4. Best-adapted survive 5. Traits passed to offspring 6. Population changes over time.

Misconceptions about evolution

Humans did not evolve from modern monkeys; individuals do not evolve, populations do; evolution is a scientific theory supported by evidence.

Microevolution

Refers to small changes within a population or species.

Macroevolution

Refers to large-scale changes over long periods, including speciation.

Cladogram

A diagram that shows evolutionary relationships, where the closest branches indicate closest relatives and shared traits appear at branch points.

Autotrophs

Organisms that make their own food, such as plants.

Heterotrophs

Organisms that eat other organisms, such as animals.

Energy flow in ecosystems

Energy is mostly lost as heat as it moves through ecosystems and is not fully recycled.

Keystone species

A species that has a major impact on its ecosystem.

Trophic cascade

A chain reaction in an ecosystem caused by changes in one trophic level.

Direct relationship

A relationship where one species affects another immediately.

Indirect relationship

A relationship where effects happen through another species, e.g., wolves eat elk leading to more plants and subsequently more beavers/birds.

Food web arrows

Indicate direction of energy flow, showing who gets eaten.

Energy pyramid components

Sun → Producers → Primary consumers → Secondary consumers → Tertiary consumers.

Population vs Community vs Ecosystem vs Biosphere

Individual = one organism, Species = organisms that can reproduce together, Population = same species in one area, Community = all populations in one area, Ecosystem = living + nonliving things, Biosphere = all ecosystems on Earth.

Secondary consumer

An organism that eats a primary consumer.

Symbiosis types

1. Mutualism: both benefit (e.g., bees + flowers). 2. Commensalism: one benefits, other unaffected (e.g., barnacles + whale). 3. Parasitism: one benefits, one harmed (e.g., tick + dog).

Biotic vs Abiotic factors

Biotic factors are living (like plants and animals), whereas abiotic factors are nonliving (like water, temperature, sunlight).

Richness vs Evenness

Richness refers to the number of species, while evenness considers how balanced populations are; evenness is important for ecosystem stability.

Predation

The act of one organism hunting another, such as a hawk eating a mouse.

Niche partitioning

Occurs when species share resources differently to reduce competition.

Human impacts on ecosystems

Negative: pollution, habitat destruction, climate change, overfishing/hunting, invasive species. Positive: conservation and reforestation.

Climatograms

Visual tools where bars represent precipitation and lines represent temperature; they help identify biomes based on temp + rainfall patterns.

Density-dependent factors

Factors that depend on population size, such as disease and competition.

Density-independent factors

Factors that do not depend on population size, such as fires and floods.

Energy loss in trophic levels

About 90% of energy is lost between trophic levels; only 10% transfers.

Human effects on ecosystems

Positive effects include conservation and reforestation; negatives include pollution, deforestation, and invasive species.

Digestive System purpose

Breaks down food and absorbs nutrients; includes esophagus, stomach, small intestine, large intestine, liver, gallbladder, and pancreas roles.

Respiratory System purpose

Exchanges oxygen and carbon dioxide; includes trachea, bronchi, and lungs.

Urinary System purpose

Removes liquid waste and balances water; roles of kidneys, ureters, bladder, and urethra.

Circulatory System purpose

Transports oxygen, nutrients, and wastes; includes ventricles, atria, veins, arteries, aorta, and vena cava roles.