7C: Populations in Ecosystems Flashcards
Define habitat
The place where an organism lives, e.g a rockpool or a field
Define population
ALL the organisms of one species in a habitat
Define community
Populations of different species in a habitat make up a community
Define ecosystem
A community + all the abiotic conditions in the area
(ecosystems can be small, e.g a pond, or large e.g an entire ocean
Define abiotic factors
The non-living features of an ecosystem
Define biotic conditions factors
The living features of the ecosystem
Give 4 examples of abiotic factors
Temperature, water levels, light and space
Give 2 examples of biotic factors
Predation and availability of food
Define niche
The role of a species within its habitat, includes:
- Biotic interactions (e.g what it eats, what it’s eaten by)
- Abiotic interactions (e.g O₂ it breathes in, CO₂ it breathes out)
Define adaptation
A feature that members of a species have that increases their chance of survival and reproduction, e.g giraffes have long necks to help them reach vegetation that’s high up.
(Animals are adapted for both abiotic + biotic conditions)
What happens if two species try to occupy the same niche?
They will compete with each other. One species will be more successful than the other, until only one species is left.
What are 3 types of adaptation?
Physiological (processes inside the body)
Behavioural (the way an organism acts)
Anatomical (structural features of their body)
What is population size?
The total number of organisms of one species in a habitat
What is the carrying capacity?
The maximum stable population size of a species that an ecosystem can support. Carrying capacity varies as a result of both abiotic + biotic factors
What happens when abiotic factors are ideal for a species?
Organisms can grow fast and reproduce successfully so population size increases
What happens when abiotic factors aren’t ideal for a species?
Organisms cannot grow fast or reproduce successfully so their population size decreases
What is interspecific competition?
Competition between different species for the same resources
What is intraspecific competition?
Competition within a species for the same resources
Describe what interspecific competition does to population sizes
- The resources available to both populations are reduced, e.g if they share the same food source there will be less available for both of them.
-This means that both populations will have limited resources, so they will have less energy for growth + reproduction
= the population sizes of both species will decrease.
Describe what happens in intraspecific competition
1) The population of a species increases when resources are plentiful. As the pop. increases, there’ll be more organisms competing for the same amount of food
2) Eventually, resources e.g food and space become limiting so the population begins to decline
3) A smaller pop. then means there’s less competition for resources (which is better for growth and reproduction) and so the pop. begins to increase again
Describe the 5 stages of the predator prey cycle
1) As prey population increases there’s more food for predators so predator population also increases.
2) More prey are eaten by the growing predator population, so the prey population begins to fall
3) With fewer prey available the predators are in greater competition with each other with the prey that are left
4) The predator population decreases as some individuals are unable to obtain enough prey to survive/reproduce
5) With few predators left less prey are eaten so prey population increases (back to 1)
Describe what predation is
The preying of one animal on others.
- In a complex food web the number of predators and prey remain relatively stable
- In a simple food chain the number of predators and prey can change
What is random sampling used for?
Used to estimate population size - must be relatively evenly distributed.
Describe how to carry out random sampling (4 steps)
1) Divide the area up into a grid and assign each square coordinates
2) Use a random number generator to choose random coordinates
3) Place the quadrats at the coordinates
4) Estimate % cover, count organisms
What is quadrat sampling used for?
To measure organism abundance - the number of individuals of a species within a given area
What is transect sampling used for?
Used to sample when organism distribution has spatial variation
Describe how you carry out transect sampling (4 steps)
1) Place a line that’s marked at regular intervals across the area
2) Place a quadrat at each interval
3) Count/calculate the % cover of organisms in each quadrat
4) Repeat with more transects and calculate the average number of organisms at each distance.
What is the % coverage?
An estimate of the area within a quadrat in which a species covers.
What type of organisms are transects + quadrats used to measure?
Non motile organisms (ones that don’t move about) and slow-moving organisms
What is mark-release-recapture used to investigate?
It is a method used to measure the abundance of more motile species
Describe the method of mark-release-recapture (5 steps)
1) Capture a sample of a species (using an appropriate technique) and count them
2) Mark them in a harmless way e.g a spot of paint
3) Release them back into their habitat
4) Wait a period of time (e.g a week), the take a second sample from the same population
5) Count how many of the second sample are marked. then calculate population size (using equation)
What is the equation for population size?
No. caught in 1st sample x no. caught in 2nd sample / no. marked in 2nd sample
What 3 assumptions must you make when using the mark-release-recapture method?
1) That the marked sample has enough time & opportunity to mix back in with the population
2) The marking hasn’t affected the individual’s chance of survival and the marking is still visible
3) There are no changes to population size (little death, immigration or migration)
In mark-release-recapture, how should the researcher mark the organisms?
In a way that does not influence the organisms behaviour or decrease its survival chances (e.g it should not increase vulnerability to predation)
What is succession?
The process by which an ecosystem changes over time
What does ‘ecosystems are dynamic’ mean?
That they are constantly changing
What are the 2 types of succession?
Primary and secondary
What sort of land does primary succession happen on?
Happens on land that’s been newly formed or exposed, there is no soil or organic material to start with
- e.g where a volcano has erupted to form a new rock surface or where sea level has dropped exposing a new area of land
What sort of land does secondary succession happen on?
Happens on land that’s been cleared of all the plants, but where the soil remains
- e.g after a forest fire or where a forest has been cut down by humans
Describe the process of primary succession (4)
1) Starts when a pioneer species (adapted to hostile conditions) colonise the new land surface (seeds + spores are released and start to grow)
2) Pioneer species alter the abiotic conditions - they die and microorganisms decompose them to form a basic soil
3) This makes conditions less hostile, e.g the basic soil helps retain water, which means new organisms with different niches can move in and grow
4) The soil becomes increasingly rich in minerals when new organisms die and are decomposed
= Increased biodiversity (more complex food webs)
What is a pioneer species? name 6 adaptations that suit their role
A species that colonises inhospitable environments.
- Asexual reproduction
- Production of seeds/spores
- Rapid germination
- Photosynthesis
- Nitrogen fixing bacteria
- Tolerance to extremes
What happens to the complexity of ecosystems as succession goes on?
They become more complex. New species move in alongside existing species, increasing biodiversity
Explain how during succession species can become ‘dominant’
At each stage different plants and animals that are better adapted for the improved conditions move in, and out-compete previous organisms = they become the dominant species
The new species may also change the environment in such a way that it becomes less suitable for the previous species.
What is the final stage of succession?
A climax community is reached
Describe a climax community
The final stage of succession. The ecosystem is supporting the largest and most complex community of plants and animals it can. It won’t change much more - its in a steady state
Describe secondary succession
Same process as primary, but in secondary there’s already a soil layer (so succession begins at a later stage - larger plants)
What is conservation?
The protection and management of ecosystems in a sustainable way
Why does conservation involve managing succession?
- Climax communities often don’t contain species that were present in earlier stages
- Due to their habitat disappearing/ being outcompeted
- By managing succession we can conserve these habitats + the species (by preventing a change to the next stage)
Why is there often conflict over conservation issues?
There’s often conflict between human needs and conservation. Careful management needs to find a balance between the two and maintain sustainability of natural resources
Give 4 examples of conservation techniques
- Seedbanks (to preserve extinct/endangered plants)
- Fishing quotas
- Protected areas e.g national parks
- Breeding endangered species in captivity to increase numbers in the wild
