Week 8 - Population ecology Flashcards by Gabriella Smith

What is the definition of ecology?

The scientific study of organisms, the interactions that determine that distribution and abundance, and the relationships between organisms and the transformation and flux of energy.
INTERACTIONS BETWEEN ORGANISM AND ENVIRONMENT

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What is population ecology?

Population ecology explores how biotic and abiotic factors influence the density, distribution, size, and age structure of populations

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What does adaption mean?

The evolutionary process whereby organisms become better suited to their environment over time

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What are the 2 explanations for why species occur where they do?

Ultimate explanation = evolutionary perspective
Proximate explanation = Here and now

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What is the ultimate explanation for why a species is where it is?

Through natural selection organisms become adapted to maximise their fitness in a particular environment

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What are the 3 different kinds of fitness ?

Direct = Numb of offspring an individual produces compared to others in the population

Indirect = How you help others related to you to contribute their genes to the next gen

Inclusive = direct and indirect

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What is the proximate explanation for why a species occurs where it does?

How biotic and abiotic factors affect where a species is here and now

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What is an example of a biotic factor?

Other organisms e.g. humans placing a rhino there

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What is the difference between intraspecific and interspecific competition?

Intra - competition between individuals of the same species ( 2 rhinos)
Inter - competition between individuals of different species

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What is an example of abiotic factors that may influence the location of a species?

Water, temperature, wind, pH, light

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What is an ecological niche ?

The role and position a species has in its environment; how it meets its needs for food and shelter, how it survives, and how it reproduces. It includes all of its interactions with the biotic and abiotic factors of its environment.

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What is the difference between a habitat and a niche?

Habitat= description of an environment
Niche = how the habitat is used

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What are the 2 types of niche ?

Fundamental - in the absence of other organisms
Realized - in the presence of other organisms

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What is the difference between acclimation and acclimatization?

Acclimatization = Occurs within a short period: It involves an organism’s physiological adjustment to environmental changes

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What is phenotypic plasticity?

The ability of an organism to change its phenotype in response to changes in the environment

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What kind of organism is phenotypic plasticity most important?

Immobile one (flowers)

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What is meant by the term life history theory?

The pattern and duration of key events in an organism’s lifetime which affect the number of offspring produced.

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What is meant by the cost of reproduction?

Resources that are used for one thing cannot be used for another

This means that an organism’s life history will reflect these trade-offs

One trade-off that is much explored is between growth and reproduction

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What is meant by K selected organisms?

Organisms which use a reproductive strategy of investing more energy into fewer larger offspring e.g. whales

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What types of environment suits K-selected organisms ?

Stable environments:
- So they can rely on a long lifespan and low mortality rate
- Can produce multiple times with a high offspring survival rate

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What are R-selected organisms?

Organisms that invest in producing quickly and early
INVEST IN REPRODUCTION NOT GROWTH

What type of environment are R-selected organisms suited to?

Unstable environments:
- Have a high mortality rate so produce lots of offspring, hope some will survive

What is the difference between deterministic and stochastic environmental change?

Deterministic changes are predictable and occur in a regular, consistent manner.

Stochastic changes are random and unpredictable, often occurring due to chance events or irregular patterns.

What is the issue and solution to measuring abundance?

Absolute (total) counts is extremely difficult even for large species living in open
- so we take samples and use indirect measure (signs they were there)

What key factors must your sample have?

Must be: - Quantitative - Comparable - Cost effective - Biologically relevant (if it's raining there won't be many pollinators)

What method is used to estimate population size?

Mark release recapture

What assumptions is the mark release recapture based on?

No migration Marking : No damage to organisms Doesn’t make them more visible to predators Doesn't make them easier to recapture

What is abundance determined by?

The combined effects of all the processes that affect a population whether they are biotic or abiotic, dependent or independent of density

What are the 3 types of distributions found in animals?

Aggregated distributions : - most common - Found in environments with patchy resources; animals “clump” around resources or clump due to social factors Uniform distributions: - Evenly spaced - maximize the space between individuals due to competition for a resources Random distributions: - Least common - Can occur in plants with wind dispersed seeds that grow in random places

Which is the most and least common type of distribution?

Most - Aggregated Least - Random

What is the equation for calculating changes in population size and what does this calculation assume?

Change in population size = Births + Immigrants – Deaths – Emigrants ASSUMES POPULATION IS CLOSED

What are the 2 types of life tables?

Cohort lift table - dynamic, follows cohort over time Static life table - snapshot of the population at one time

What do survivorship curves show?

Show the pattern of survival for a population or species over time, typically grouped into different age classes

What type of survivorship curve would you see for a k-selected organism?

High survival rates through life - drops at very end

What type of survivorship curve would you see for r-selected organisms

High mortality rates throughout life

When resources are unlimited what is the population growth rate?

Geometric - seasonal/pulsed reproduction or Exponential - continuous reproduction (happens at any time)

When resources are depleted what happens to growth rate?

Logistic/sigmoidal growth occurs =starts off exponential and slows down as resources are used. Population growth plateaus at the carrying capacity (K).

What is meant by intrinsic growth rate (r)?

Means a population grows its fastest when it's small and resources are abundant

What factors influence population growth?

Density-dependent factors Density-independent factors

What are some examples of density-dependent factors?

Competition Disease Predation Territoriality

How do the effects of density-dependent factors change with population size

Effects of these factors increase with size e.g. increasing population means disease spreads faster in dense populations.

What is meant by Negative density dependence ?

Growth slows with crowding

What is the Allee effect and what can it cause?

Low growth at low density (trouble finding mates or pollinators). Can cause functional extinction

What are Density-independent factors?

Factors that affect the population regardless of its size

What are some examples of density independent factors?

Climate extremes Pollution Catastrophes

What is meant by the term regulation?

Population returns to a stable size due to density-dependent feedback - called true regulation

What is meant by the term Determination?

Current population size reflects all influences (both dependent and independent)

What is Maximum Sustainability Yield (MSY)?

The largest harvest that can be taken sustainably without population decline

What is the goal of MSY?

To keep population size where growth is maximal

What are some problems with Maximum sustainability yield?

Hard to estimate true population size or carrying capacity. Ignores: Age, size, and reproductive status of individuals Ecosystem-level effects, bycatch, and species interactions Other mortality factors (e.g. disease, predation) Has caused collapse of many fisheries