Topic 7C: Populations in Ecosystems Flashcards
Definition: Ecosystem
All of the living organisms in a community, plus all the non-living conditions in the area in which they live.
Definition: Biotic conditions
The living-features of an ecosystem.
Definition: Abiotic factors
The non-living features of an ecosystem.
Definition: Habitat
The place where an organism lives within an ecosystem.
Definition: Niche
The role of a species within its habitat, which can be explained in two categories - it’s biotic interactions, and it’s abiotic interactions.
Niche: Biotic interactions
What the organism eats, or is eaten by etc.
Niche: Abiotic interactions
The temperature range an organism lives in, the time of day it eats etc.
What are the features of a niche?
- Every species has a unique niche.
- If two species try to occupy the same niche, one species will outcompete the other meaning the other species won’t be able to survive.
Definition: Adaptation
A feature which members of a species have that increase their chances of survival and reproduction.
What are the different types of adaptations?
• Physiological:
Processes inside the organisms body.
• Behavioural:
The way the organism acts.
• Anatomical:
Structural features of the organisms body.
Definition: Population
All of the organisms of one species in a habitat.
Definition: Community
Made up of the different populations in a habitat.
Definition: Carrying capacity
The maximum stable population size of a species that an ecosystem can support.
How do abiotic factors affect population size?
- If abiotic conditions are ideal for a species, organisms can grow quicker and reproduce more successfully.
- If abiotic conditions are not ideal for a species, organisms cannot grow as fast or reproduce as successfully.
How do biotic factors affect population size: Interspecific competition
1) Organisms of a different species compete for the same resources.
2) Resource availability for each population is reduced.
3) Therefore, organisms have less energy for growth and reproduction, so the population size of each species decrease.
4) One species will be better adapted to the environment and so outcompete the other.
How do biotic factors affect population size: Intraspecific competition
1) Organisms of the same species competed for the same resources.
2) This causes a cyclical change in population size around the ecosystem’s carrying capacity.
3) When resources are plentiful, population size increases.
4) However, because there are more organisms within the population, resources become limited and the population size falls.
5) Then, there is less competition, so population size increases once again.
How do biotic factors affect population size: Predation
1) One organism (predator) eats another (prey).
2) As the prey population decreases, there isn’t enough food to support the predator population, so the predator population size falls.
3) Therefore, the prey population increases, which means there is more food availability for the predators.
4) This allows the predator population to increase once again, meaning more prey are being fed on, and the prey population falls.
How do you investigate population growth in bacteria?
1) Produce a broth culture containing bacteria
2) Pass light through the broth culture.
3) Use a spectrophotometer to measure the absorbable value.
4) Repeat at regular time intervals.
The more bacteria present in the culture, the less light will pass through and be detected by the spectrophotometer, producing a higher absorbance value.
Definition: Abundance
The number of individuals of one species in a particular area.
How is abundance measured?
- Counting the number of individuals in a sample.
- Finding the frequency by calculating the percentage of samples in which the species was present.
- Finding the percentage cover of the sample.
Definition: Distribution
Where a particular species is within an area which you are investigating.
How do you carry out random sampling?
1) Choose an area to sample using a random number generator to avoid bias.
2) Take a sample of the population using a technique such as a quadrat.
3) Repeat the process to increase reliability.
4) Calculate an estimate for the distribution of the whole area.
Methods for investigating population: Quadrats
1) Randomly place on ground at different places to avoid bias.
2) Record the species frequency in each location.
Methods for investigating population: Transects
1) Place quadrats side by side or at regular intervals along a line.
2) Measure how species frequency changes from one quadrat to the next.
Methods for investigating population: Capturing motile organisms
1) Use a net or pitfall trap to capture organisms.
2) Investigate any organisms you have captured.
Why is the mark-release-recapture method used?
To measure the abundance of more mobile species.
How do you carry out the mark-release-recapture method?
1) Capture a sample of a species and count them.
2) Mark then in a harmless way before releasing them back into their habitat
3) After a period of time, take a second sample from the same population.
4) Count how many of the second sample are marked and use the equation to estimate the total population size.
Mark-release-recapture: Equation
Total population size = (no. caught in first sample x no. caught in second sample) / no. marked in second sample
What does the accuracy of the mark-release-recapture method depend on?
- Marked sample must have enough time to mix back in with original population.
- Marking mustn’t affect chances of survival.
- There mustn’t be any changes in population size during study.
Definition: Succession
A process by which an ecosystem changes over time, as one community of organisms is replaced by another.
What is the process of primary succession?
1) A pioneer species colonise the area.
2) Pioneer species die and are decomposed by microorganisms, which produces soil.
3) This makes conditions more favourable for a new species, which move in and out compete the old species.
4) This increases diversity as the conditions become less hostile.
What limits the size of a climax community?
- Availability of sunlight/nutrients for LDR’s of photosynthesis, which provide energy for consumers.
- Disease.
- Predation.
- Competition for food/space.
What is secondary succession?
The same as primary succession but there is already a layer of soil present (e.g. after deforestation) meaning the pioneer species is often larger.
What are the human impacts on succession?
- Human activities can prevent succession, meaning a climax community will not be produced.
- Instead, a plagioclimax is produced.
Definition: Conservation
The protection and management of species and habitats in a sustainable way.
Definition: Sustainable
Enough resources are used to meet the needs of people today, without reducing the ability of people in the future to meet their own needs.
Conservation methods: Management of succession
Succession is prevented in order to preserve an ecosystem in its current stage of succession.
Conservation methods: Seed banks
- A seed bank is a store of seeds from lots of different plant species, which act as a back up for the conservation of plant species in the wild.
- Large amounts can be conserved in a small area, and can be stored anywhere in the world for long periods of time.
Conservation methods: Captive breeding
- Captive breeding programmes involve breeding animals in a controlled environment, so that endangered species can be bred in captivity to help increase their numbers.
- These animals can then be reintroduced to the wild, increasing the natural population.
Conservation methods: Fishing quotas
- Fishing quotas are limits to the amount of certain fish species that fisherman are allowed to catch, reducing the number of fish being captured and killed.
- Fisherman are unhappy with quotas as it limits their possible income and dead fish are often discarded.
Conservation methods: Protected areas
• Protected areas protect habitats and the species in them by restricting industrial developments and farming.
