quiz questions bio 148

Population (ecology)

A group of individuals of the same species living in a particular area and interacting with one another

Ecology levels

Study of biological organization (individual → population → community → ecosystem)

Abundance

Number of individuals in a population

Distribution

Where individuals are located in a population

Population density

Number of individuals per unit area

Key ecological question

What determines the abundance and distribution of a species?

Conservation biology link

Understanding populations helps protect species and ecosystems

Counting populations

Estimating number of individuals in a population

Why counting is difficult

Some organisms are hard to distinguish or highly mobile

Ways to estimate abundance

Distance sampling, mark-recapture, quadrat sampling

Distance sampling

Method where individuals are observed from a transect and distance is measured

Detection function

Probability of detecting an organism decreases with distance

Mark-recapture method

Capture, mark, release, and recapture individuals to estimate population size

Mark-recapture formula

N = (C1 × C2) / R

Quadrat sampling

Method for sessile organisms using plots to estimate density

Sampling effort

Amount of sampling affects accuracy of estimates

Species range

Geographic area where a species is found

Why species aren’t everywhere

Habitat suitability, history, and dispersal

Habitat suitability

Abiotic conditions must meet species’ needs

Species Distribution Models

Predict where species can live based on conditions

Historical factors

Evolutionary and geological history affect distribution

Example (polar bears)

Evolved from grizzly bears → not found in Antarctica

Dispersal

Movement of individuals into (immigration) and out of (emigration) populations

Migration

Seasonal round-trip movement of populations

Dispersal ability varies

Some species move far, others very little

Example dispersal (plants)

Seeds may travel short distances or be carried by animals

Example dispersal (coconuts)

Can float long distances and still germinate

Metapopulation

Group of separated populations connected by dispersal

Dispersion

Spatial arrangement of individuals in a population

Importance of dispersal

Maintains genetic diversity and allows recolonization

Patch dynamics

Local populations may go extinct but are recolonized

Habitat fragmentation

Human-caused division of habitat into smaller patches

Effect of fragmentation

Increases risk of population collapse

Population dynamics

Changes in population size over time

Patterns of change

Stable, increasing, decreasing, or fluctuating

Exponential growth

Rapid growth at a constant proportion under ideal conditions

Limitation of exponential growth

Resources eventually run out

Logistic growth

Growth that slows as population reaches carrying capacity

Carrying capacity (K)

Maximum population size environment can sustain

Density dependence

Population growth slows as population size increases

Population fluctuations

Population size varies due to environmental conditions

Population cycles

Regular increases and decreases in population size

Small population risks

More vulnerable to extinction

Extinction vortex

Small populations become progressively smaller

Effective population size

Individuals contributing to next generation

Genetic problems

Loss of genetic diversity and inbreeding

Low genetic diversity

Reduces adaptability and fitness

Demographic problems

Random events impact small populations more

Allee effect

Growth rate decreases at low population density

Environmental risks

Weather, disasters, and variability impact survival

Small populations risk

More likely wiped out by environmental change

Key takeaway (population)

Group of individuals with abundance and distribution

Key takeaway (metapopulation)

Connected populations via dispersal

Key takeaway (range)

Determined by conditions, history, and dispersal

Key takeaway (growth)

Exponential, logistic, or cyclic

Key takeaway (risk)

Small populations vulnerable to extinction

Key life history events

Reproduction, survival to adulthood, and metamorphosis (all are key events)

Advantage of sexual reproduction

Creates genetic diversity (unlike asexual reproduction which creates clones)

Complex life cycle definition

A life cycle involving at least two distinct morphological, physiological, or habitat stages

Do some species use both sexual and asexual reproduction?

True

Bird reproductive strategy

Birds raise the maximum number of chicks they can successfully bring to fledglings

K-selected species

Large, long-lived, provide parental care, produce fewer larger offspring

Life-history trade-off (offspring size vs survival)

Larger offspring can reduce parental survival

Life-history trade-off (offspring number vs size)

More offspring usually means smaller size per offspring

Life-history trade-off (offspring number vs parental growth)

More reproduction reduces energy for parent growth

Life-history trade-off (care vs future reproduction)

Caring for offspring can reduce ability to reproduce again

Arctic vs San Francisco plants

Arctic plants grow and reproduce quickly; SF plants grow slower and may live multiple years

Clownfish strategy

Limit growth to avoid conflict with larger individuals and avoid eviction

Optimal foraging theory core principle

Animals forage in a way that maximizes energy intake per unit of time spent foraging

Best group size for individuals

Intermediate group size

Disadvantages of group living

Time spent in social hierarchy, competition for food, and disease risk (all of the above)

Not a core animal behavior research question

How animals decide when to metamorphose

Sexual selection definition

Natural selection favoring traits that increase reproductive success in one sex

Ecological community

All the species in an ecosystem (correct definition)

Species diversity components

Species richness and evenness of abundances

Why sampling effort matters

Most species are rare, so low sampling misses many species

Trophic level

A group of species that eat similar prey and are eaten by similar predators

Indirect interactions

One species affects another through a third species

Keystone species example

Sea otter

Community diversity comparison

A community with more even species abundances has higher diversity

Darwin cats hypothesis

Cats eat mice, mice eat bees → cats benefit pollination

Species composition

The specific species present and their relative abundances; affects how communities function

Foundational species

Large or dominant species that shape communities through habitat or resource provision

Succession (ecology)

The change in a community's species composition through time

Succession stressor intensity

High intensity

Key processes of succession

Local extinction and colonization

Ulva–Gigartina interaction

Ulva facilitates the growth of Gigartina

Reverse succession

Yes, disturbances can move communities backward

Models of succession

Facilitation, tolerance, inhibition

Primary succession examples

After glacier retreat, volcanic eruption, or new habitat formation (all)

Herbivores in succession

They can prevent succession by limiting recruitment of late-arriving species

Primary succession conditions

High intensity, low frequency, large spatial extent disturbances

Secondary succession conditions

Low intensity disturbances with smaller spatial extent (can vary in frequency)

Little successional change conditions

Medium intensity, medium frequency, medium spatial extent