3.3.1- The effect of biotic and abiotic factors on populations

What is an individual?

Single member of species

What is population?

Population - Individuals of same species in the same area at the same time.

What is Community?

Community - multiple populations (of different species) living and interacting in the same area.

What is Ecosystem?

Ecosystem - The interaction between a community ( the living, biotic part) and the non-living (abiotic) parts of the environment.

What is Biosphere?

Biosphere - The region above, on and below the earth where living organisms are.

Habitat

The place where a species lives within an ecosystem.

Niche

The role that a species plays within its habitat, including biotic interactions (e.g., feeding on other species) and abiotic interactions (e.g., exchanging gases with the atmosphere).

Competitive Exclusion Principle

A niche can only be occupied by one species; if two species try to occupy the same niche, they compete for resources, and one will out-compete the other.

What can the changes that species produce in the abiotic environment result in?

The changes that species produce in their abiotic environment can result in a less hostile environment.

Carrying Capacity

The maximum stable population size of a species that an ecosystem can support.

What limits the population size?

There are many abiotic and biotic factors that prevent every individual from making it to adulthood and reproducing. This ensures the population size of each species is limited at one point.

Which part of a population graph indicates the carrying capacity?

The point at which the graph starts to plateau is the carrying capacity. This is the part where the environmental factors kick in and slow down the rate of population growth.

Abiotic Factors Affecting Population Size

Light, water, temperature Temperature (mammals would have to use up more energy to maintain their optimum body temperature so they have less energy available for growth and reproduction. Population growth is limited)., space, soil pH

Biotic Factors Affecting Population Size

Interspecific competition, intraspecific competition, predation.

Interspecific Competition

Competition for the same resources between individuals from different species.

Intraspecific Competition

Competition for the same resources between individuals from the same species.

Predation

Consumers who kill and eat other animals are known as predators.

What happens to the number of predators and prey in a stable community?

In a stable community the number of predators and prey rise and fall in cycles limiting the population sizes of both predators and prey.

Describe the rise and fall in predator and prey population

The number of predators increases as there is more prey available.
The number of prey then decreases as there are now more predators.
The number of predators decreases as there is now less prey available.
The number of prey increases as there are now fewer predators.
The cycle now repeats.

What do fluctuations caused by external factors create?

Selection pressure.

What is selection pressure?

an evolutionary force that causes a particular phenotype to be more favorable in certain environmental conditions

The three phrases in a population Growth Curve

Typically have three phases: slow growth, rapid growth, and a plateau where growth stabilizes.

Describe slow growth

Period of slow growth - small initial number of individuals that reproduce slowly to build up their numbers

Describe rapid growth

A period of rapid growth where the ever-increasing number of individuals continue to reproduce. The population size doubles during each interval of time.

Describe the plateau

A period when the population growth declines until its size remains more or less stable. (Decline may be due to limited food size or increased predation.) The graph then level out and fluctuates due to variations in other factors.

Sampling Methods

Random: Sampling points determined by chance. Systematic: Sampling points chosen deliberately, possibly leading to bias.

What are the three sampling methods?

Quadrats
Transects
Mark-release-recapture

Quadrats

Used in sampling to measure species abundance and distribution.

Transects

Used in systematic sampling to show how species distribution or abundance changes with different physical conditions.

Mark-Release-Recapture

A method for estimating population size by capturing, marking, releasing, and recapturing individuals.

What factors do you need to consider when using a quadrat?

The size of the quadrat, the number of quadrats, and the position of each quadrat.

What is the distribution of a species?

The distribution of a species describes how it is spread throughout the ecosystem

What is the abundance of a species?

The abundance of a species is the number of individuals of that species.

What is species frequency?

The probability that the species will be found within any quadrat in the sample area.

Formula for species frequency?

Number of quadrats species will be found within/ total number of quadrats *100

What is percentage cover?

Percentage cover - The quadrat is divided into 100 smaller squares, the number of squares the species is found in is equivalent to its percentage cover in that quadrat.

When do you use belt transects and systematic sampling?

There can be changes in physical conditions, using systematic sampling is more appropriate here.
Transects help show how the distribution or abundance of a species changed with the different physical conditions in the area.

How do you use belt transects?

Place quadrats at regular intervals and record the percentage cover.

Describe mark release recaptur

Large sample is taken, the number of individuals is counted and then marked (in a way where it won't affect their survival)
The marked individuals are then returned to their habitat and allowed to mix
After a sufficient amount of time has passed another large sample is captured. The number of individuals as well as the number of marked individuals is marked

Formula for mark release recapture?

Formula:
Estimate of population = number of marked individuals in first sample * number of individuals in the second sample / number of marked individuals in the second sample.

Asumptions for mark and recapture

Assumptions:
The marked individuals are given sufficient time to disperse and mix back in fully
The marking doesn't affect the survival rates of the marked individuals.
The marking remains visible throughout the sampling process and doesn't rub off
The population stays the same size (no migrations, births, deaths.)

What are two major processes in an ecosystem?

The flow of energy through the system
The cycling of elements within the system

Do ecosystems stay the same forever?

Both biotic and abiotic components within ecosystems are dynamic and constantly changing.

Succession

Change in the community over time, including primary succession (newly formed land) and secondary succession (land that has sustained life but is altered).

How can new uninhabited land be created?

This new uninhabited land can be created by: magma when volcanoes cool, sea levels dropping

What is the first stage of primary sucession?

Seeds and spores are carried by the wind and land on the exposed rock. They begin to grow. These first species to colonise the new land are known as pioneer species (species that can colonise bare rock or ground. As they die and decompose the dead organic matter (humus) forms a basic soil.

Second stage of primary sucession?

Seeds of small plants and grasses (intermediate species) are also carried by the wind or by faeces. These land on this basic soil and begin to grow. (These plants are adapted to survive in shallow, relatively nutrient-poor soils.)
As these small plants and shrubs die and decompose, the new soil becomes deeper and more nutrient-rich. The roots of these small plants and shrubs also form a network that helps hold the soil in place and prevents it from being washed away.

Third stage of sucession?

Larger plants and shrubs (as well as small trees) begin to grow. Finally, the soil is deep, contains enough nutrients and holds enough water to support the growth of large trees. This final species becomes the dominant species.

Final stage of primary succession?

The final community is now formed, containing all the different plant and animal species. This is known as the climax community (a stable, final community that exists in a balanced equilibrium).

What is the difference in secondary sucession?

In secondary succession (land that has already sustained life is altered) it follows the same system however it is quicker. This is because the spores and seeds often remain alive in the soil and there an influx of animals and plants through dispersal and migrations

Pioneer Species

First species to colonize new or barren environments;

What are characteristics of pioneer species?

Large production of seeds that can travel by the wind
Rapid germination
Ability to photosynthesise
Ability to fix nitrogen from the atmosphere
Tolerance to extreme conditions.

What does succession lead to?

Less hostile
Greater number + variety of habitats
More complex food webs
Increases stability of the community
Increases biomass

What happens at after every stage of sucession?

At each stage, certain species gradually change the local environment so it becomes more suitable for other species. The new colonising species then changes the environment in a way that it becomes less suitable for the previous species.

Climax Community

A stable, final community that exists in a balanced equilibrium after succession.

Conservation

The protection and management of species and habitats in a sustainable way.
Sustainable use of ecosystems means using these resources in a way that meets the needs of humans alive now without reducing the ability of future humans to meet their own needs.

Why could preventing an area from reaching its climax community be good?

Sometimes preventing an area from reaching its climax community can be a good thing as ecosystems at intermediate stages hold a distinct diversity.

How do you prevent sucession?

Ways to prevent succession :
Grazing animals.
Managed burning.

Why are logarithmic scales used in population graphs?

As populations can increase at rapid rates, it can be hard to use large numbers in a linear scale. This is why logarithmic scales are used. It displays a larger number of values on a single graph.

Sustainable Use of Ecosystems

Using resources in a way that meets the needs of current humans without compromising the ability of future generations to meet their own needs.

Conserved Areas examples

National parks, marine parks.

Conservation in captivity

Zoos
Invaluable resource for scientific research.
Captive breeding
Captive breeding can reduce genetic diversity. Not all zoos can provide adequate habitats for animals with specific needs.
Botanic gardens (plant equivalent of zoos
Zoos and botanic gardens are instrumental to education.

What are frozen zoos?

Frozen zoos - store genetic material from animals at very low temperatures so they can be kept for a very long time. In the future, genetic materials from extinct animals could be used to breed and reintroduce a species through IVF and genetic engineering.

What are seed banks?

A seed bank - conserves plant diversity by drying and storing seeds in a temperature controlled environment