Bio150 Exam 5

Levels of ecological organization

Individual (organism), Population, Community, Ecosystem.

Population

A group of individuals of the same species living in the same area.

Community

All the species that interact in a given area.

Ecosystem

All organisms in a community plus the abiotic environment.

Proximate vs. ultimate mechanisms

Proximate = how a behavior occurs; Ultimate = why it increases fitness.

Learning and flexibility in behavior

Behaviors vary from innate to learned and from stereotyped to condition‑dependent.

Condition‑dependent behavior

Behavior that changes with environmental or social conditions; can still be genetically controlled.

Cognition vs. learning

Learning is behavior change from experience; cognition is forming new associations or insights.

When behaviors persist

Behaviors persist when benefits to fitness exceed costs.

Honest communication example

Honeybee waggle dance or bluegill sunfish mating signals.

How altruism persists

Through inclusive fitness; Hamilton's Rule (Benefits × Relatedness > Costs).

Kin selection

Helping relatives reproduce to increase shared genetic success.

Helping non‑relatives

Reciprocal altruism — exchanging fitness benefits over time.

I + B = D + E

Population grows when immigration + births > deaths + emigration.

Measuring population size

Visual counts, sampling/extrapolation, and mark‑recapture.

Age structure and demography

Shows growth potential: many young = growing; few young = declining.

Survivorship curves

Humans = Type I; Beavers = Type II; Rabbits = Type III.

Offspring investment differences

Species differ due to life‑history tradeoffs between survival and reproduction.

Semelparity vs. iteroparity

Semelparity = reproduce once; Iteroparity = reproduce repeatedly.

Growth vs. carrying capacity

Growth is rapid below K and slows as resources become limited near K.

Food decline and carrying capacity

Reduced food lowers K and causes population decline or oscillation.

Factors limiting population growth

Resource depletion, predation, disease/parasites, stress (density‑dependent).

Interspecific interactions

Competition (-/-), Mutualism (+/+), Consumption (+/-), Commensalism (+/0).

Interference vs. exploitation competition

Interference = direct confrontation; Exploitation = indirect resource use.

Consequences of similar niches

Competitive exclusion — stronger competitor eliminates the other.

Fundamental vs. realized niche

Fundamental = possible niche; Realized = actual niche after interactions.

Müllerian vs. Batesian mimicry

Batesian = harmless mimics harmful; Müllerian = harmful species resemble each other.

Snowshoe hare cycles

Driven by predator-prey dynamics and density‑dependent predation.

Predictability of communities

Communities are not fully predictable; chance events matter.

Succession influences

Influenced by species present, interactions, and local conditions.

Panama vs. Wisconsin diversity

Panama has higher diversity because diversity increases toward the equator.

Disturbance and diversity

Intermediate disturbance leads to highest species diversity.

Resistance vs. resilience

Resistance = how affected by disturbance; Resilience = how quickly it recovers.

Productivity definition

Biomass produced per unit time (g/m²/yr).

Diversity and productivity

More species → higher productivity.

Why species‑rich habitats are resistant

Diverse systems resist disturbance and recover faster.

Climate features determining biomes

Temperature and precipitation.

Four ecosystem components

Producers, consumers, decomposers, abiotic environment.

Food chain terms

Autotroph = producer; Heterotroph = consumer; Primary consumer = herbivore; Secondary consumer = carnivore.

Why food chains are short

Energy loss at each trophic level (~90%).

Pyramid of productivity

Shows decreasing energy at higher trophic levels.

Limits on terrestrial NPP

Temperature and water availability.

Most productive biome

Tropical rainforest.

Mercury fish advisories

Biomagnification increases mercury in top predators.

Decomposition and nutrient cycles

Decomposition rate controls nutrient movement.

Human impact on carbon cycle

Fossil fuels and deforestation increase atmospheric CO₂.

Global warming effects on animals

Amphibian extinctions, earlier bird breeding, habitat loss.

Human impact on nitrogen cycle

Fertilizer runoff causes algal blooms and dead zones.

Nitrogen fixing

Bacteria convert N₂ into usable nitrogen (NH₄⁺ or NO₃⁻).

Dead zone formation

Nutrient runoff → algal bloom → decomposition → oxygen depletion.

Main causes of extinction

Habitat destruction (major), overhunting, exotic species.

Why island species are vulnerable

High endemism, low defenses, small populations, invasive species.

Habitat fragmentation impacts

More edge, less interior, lower quality, more predators, lower productivity.

Edge effects

More sunlight/wind and more predators/parasites at habitat edges.

How biodiversity increases productivity

More species → better nutrient use, fewer invasions, higher biomass.

Biodiversity hotspots

Small regions with extremely high species richness and endemism; conservation priority.