bio first test

Autotroph

Organisms that make their own food.

Heterotroph

Organisms that need to get energy from other organisms.

Marine food chain example

Plankton $\rightarrow$ Krill $\rightarrow$ Squid $\rightarrow$ larger predator (such as a fish or whale).

Component storing most energy in food webs

Producers.

Ecological role of grass and pine seeds

Making energy (they act as producers).

Density-independent factors

Factors such as natural disasters, habitat degradation, hurricanes, floods, fires, or droughts that affect population size regardless of density.

Density-dependent factors

Factors such as disease, famine, competition for food, predation, or overcrowding that affect population size based on density.

Calculation of $r$ value for an osprey population with birth rate 13 and death rate 3

$13 - 3 = 10$ ($r = 10$).

Hare growth rate in 1954 (lynx-hare chart)

180 (or the calculated difference based on data).

Approximate carrying capacity for lynxes (lynx-hare chart)

Around 20.

Exponential growth

Population growth that occurs when a population has unlimited resources.

Logistic growth

Population growth that occurs when resources run out and growth slows or stops.

Predator-prey relationship between wolves and moose

Wolves control or over-prey on the moose population through predation.

Three basic patterns of population dispersion

Random, Uniform (even), and Clumped.

Information provided by population dispersion patterns

Availability of mates, protection from predators, hunting patterns, and resource distribution.

Reason for uniform dispersion

Resource competition leading individuals to live independently and space themselves out.

Reason for clumped dispersion

Uneven resource distribution, searching for food, or social reasons.

Four main factors affecting population size

Birth, death, immigration, and emigration.

Population density

The number of individuals in a population living within a given area.

Percentage of energy transferred between trophic levels

Approximately $10\%$.

Typical units used to measure ecological energy

Calories, joules ($J$), or kilocalories ($kcal$).

Trophic level containing the most energy

The first / producer level (at the bottom of the pyramid).

Fate of energy during consumption

Most is used for life processes (movement, growth) or lost as heat; only a small portion is stored.

Typical trophic levels and example organisms

1st (Producer): sunflower seeds/plants; 2nd (Primary consumer): mouse; 3rd (Secondary consumer): snake; 4th (Tertiary consumer): hawk; 5th (Quaternary consumer): fox.

Food chain

The linear path of energy flow through an ecosystem, represented by arrows.

Three main categories of consumers

Herbivores (eat plants), Carnivores (eat meat), and Omnivores (eat both plants and animals).

Detritivores and decomposers

Organisms (e.g., earthworms, vultures, bacteria, fungi) that obtain energy from dead or decaying organic matter and recycle nutrients back into the ecosystem.

Biomass pyramid

A diagram representing the total amount of living tissue (organic matter) available at each trophic level.

Law of conservation of matter in ecosystems

Matter is neither created nor destroyed, but it can transform and be passed through biogeochemical cycles.

Three essential biogeochemical cycles

Water cycle, carbon cycle, and nitrogen cycle (phosphorus is also commonly included).

Processes that return carbon to the atmosphere

Cellular respiration, combustion of fossil fuels, and decomposition/erosion.

Reason for two-way $CO_2$ movement in plants

Plants absorb $CO_2$ for photosynthesis and release $CO_2$ during cellular respiration.

Origin of fossil fuels

Dead organisms buried and transformed under extreme heat and pressure over millions of years.

Percentage of atmospheric nitrogen

Approximately $78\%$ ($N_2$).

Organisms that convert atmospheric nitrogen into usable forms

Soil bacteria (nitrogen-fixing bacteria such as Rhizobia).

Main steps of the nitrogen cycle

Nitrogen fixation ($N_2$ to ammonia), Ammonification (organic matter to ammonia), Nitrification (ammonia to nitrites/nitrates), Assimilation (plant absorption of nitrates), and Denitrification (nitrates back to $N_2$ gas).

Biological molecules requiring phosphorus

$DNA$, $ATP$, phospholipids, and proteins.

Primary environmental reservoir for phosphorus

Rocks and soil (it does not enter the atmosphere).

Medium into which decomposers release phosphorus

Soil or water.

Condensation product in the water cycle

Clouds.

Precipitation

The process where condensed water vapor turns into liquid or solid and falls to Earth (rain, sleet, snow).

Runoff

Surface water found on land that eventually flows back into oceans or lakes.

Driver of daytime evaporation and transpiration

Solar heat warming the atmosphere and land.

Ecological succession

The gradual process by which ecosystems change and develop over time.

Primary succession

Succession occurring in an area where no soil previously existed (e.g., bare rock, volcanic lava), initiated by pioneer species like lichens.

Secondary succession

Succession occurring in an area where soil remains after a disturbance (e.g., after a forest fire or agricultural abandonment).

Example of secondary succession

Regrowth of life after a forest fire or in an abandoned field.

Levels of ecological organization from smallest to largest

Organism $\rightarrow$ Population $\rightarrow$ Community $\rightarrow$ Ecosystem $\rightarrow$ Biome $\rightarrow$ Biosphere.

Species

A group of similar organisms that can interbreed and produce fertile offspring.

Population

A group of organisms of the same species living in the same area and interbreeding.

Community

All the populations of different species that live and interact in a defined area.

Ecosystem

All the living (biotic) and non-living (abiotic) factors in a defined area interacting with each other.

Biome

A large geographic region characterized by its climate, plant communities, and animal adaptations (e.g., tundra, desert, rainforest).

Biosphere

The region of Earth that supports life, encompassing all ecosystems.

Habitat

The specific environment where an organism lives, including its biotic and abiotic conditions.

Abiotic factors

Non-living components of an ecosystem (e.g., temperature, sunlight, water, soil, climate).

Biotic factors

Living components that affect an ecosystem (e.g., plants, animals, bacteria, competition, predation, disease).

Interaction between biotic and abiotic factors

Abiotic factors (water availability, temperature) directly influence living organisms (e.g., bullfrogs), which also interact with biotic factors like food sources and predators.

Two categories of factors composing a habitat

Biotic and abiotic factors.

Definition of population (in population dynamics)

All the members of one species living in one place at one time.

Three general parameters describing populations

Population size, population density, and population dispersion.

Primary productivity

The rate at which producers generate biomass or energy in an ecosystem.

Limiting nutrients

Nutrients in short supply that restrict primary productivity or overall ecosystem growth.

Three key nutrients in agricultural fertilizers

Nitrogen ($N$), phosphorus ($P$), and potassium ($K$).

Direction of energy flow in an ecosystem

One direction (from the sun to producers and then to consumers).

Trophic level containing most ecosystem biomass

The first trophic level (producers).

Interdependence

The reliance of every organism on other living organisms and their environment to survive.