7C - Populations in Ecosystems Flashcards
What is a ‘habitat’?
- place where an organism lives
What is a ‘population’?
- all the organisms of one species in a habitat
What is a ‘community’?
- populations of different species in a habitat
What is an ‘ecosystem’?
- a community plus all the non-living (abiotic) conditions in the area in which it lives
What are abiotic conditions?
- non-living features of ecosystem e.g temperature and water availability
What are biotic conditions?
- living features of ecosystem e.g predators
What is a ‘niche’?
- role of a species within its habitat e.g. what it eats, where and when if feeds
What is meant by an ‘adaptation’?
- a feature that members of a species have that increases chance of survival and reproduction
How many species can occupy one niche?
- one
What happens if two species try to occupy a niche?
- they will compete with each other until only one is left
Which two conditions do organisms need to adapt to?
- biotic and abiotic
What are the three types of adaptations?
- structural
- behavioural
- physiological
3 examples of abiotic adaptations
- Otters having webbed paws to swim
- Seals having a thick layer of blubber to keep them warm
- Hedgehogs hibernating to conserve energy
3 examples of biotic adaptations
- Sea otters use rocks to smash open shellfish
- Male frogs use mating calls to attract females of the same species
- Bacteria produce antibiotics to kill other bacteria to remove competition
What can affect population size abiotically?
- The abiotic conditions can limit how large a population can grow such as food and water availability
What are the three biotic factors affecting population size?
- Intraspecific competition
- Interspecific competition
- Predation
How does intraspecific competition affect population size?
- If two species compete within the same niche, resources are limited
- meaning both population sizes are more limited until the better adapted species outperforms the other and survives
How does interspecific competition affect population?
- If there aren’t many organisms of a species in a habitat they have lots of resources so are able to reproduce but they reproduce too much so now there are too many organisms so the number of organism fluctuates above and below the carrying capacity
How does predation affect population size?
- As prey population increases there is more food for predators so that population increases
- However as predator population increases then more prey is eaten but then there isn’t enough food so predator population falls
What is the carrying capacity?
- The maximum stable population size that an ecosystem can support
Why the predator-prey more complicated that conveyed in the predation idea?
- Predation isn’t the only thing that reduces prey population size
How do you generally take a random sample?
- Choose an area to sample
- Use a random number generator to generate coordinates within the area
- Use an appropriate technique to take a sample
- Repeat this process and calculate an average and multiply it by the size of the area
What are the two non-motile methods of sampling?
- quadrats
- transects
Describe how quadrats can be used to sample.
- A quadrat is a square frame split into 100 squares by strings, you place it at different points in the area and the species frequency is how often a species is found in each quadrant
- You can also calculate percentage coverage in the quadrat by the number of squares which have more than half covered
How can transects be used for sampling?
- If you use transects to see how things are distributed across an area, you put a transect across an area
- belt transect with quadrats placed all along the transect
- or a interrupted belt transect where there are quadrats places at intervals along the transect
What is the method for sampling motile species?
- mark-release-recapture
Describe how to carry out a Mark-Release-Recapture investigation
- Capture a sample using a appropriate technique such as a trap
- Mark then in a harmless way
- Release them into the habitat
- Wait a week and take a second sample
- Count how many of the second sample are marked and you can figure out the population size from pop = (1st sample size x 2nd sample size)/number marked in 2nd sample
What assumptions are made in the Mark-Release-Recapture method?
- The sample has enough time and opportunity to mix back in with the population
- The marking hasn’t affected the chance of survival and its still visible
- There are no changes in population size due to birth death migration etc
What is succession?
- the process by which an ecosystem changes over time
What are the two types of succession?
- primary and secondary
What is primary succession?
- succession that occurs on surfaces where no soil exists
What is secondary succession?
- Succession following a disturbance that destroys a community without destroying the soil
Describe what happens during primary succession.
- Seeds and spores (pioneer species) blow on to the land and begin to grow, abiotic conditions are harsh so only pioneer species can grow
- once these die they decompose and add to the basic soil making the conditions less hostile so more species can grow which die and add further to the soil
- newer species can actually change the environment so that other species can’t grow anymore
Describe how secondary succession occurs.
- Secondary succession starts with soil so the pioneer species are larger plants
- becomes more and more complex with species competing to become dominant as biodiversity increase
- most complex community is called the climax community which won’t change much
How do climax communities vary for different ecosystems?
- The climax community for a particular climate is called the climatic climax e.g. in a temperature climate there’s more water available and milder temperatures so larger trees can exist however in polar climates there’s not much water available, low temperatures and extreme climate so the climatic climax only contains herbs or shrubs
What is a plagioclimax?
- When succession is stopped artificially
How does conservation involve managing succession?
- Often some climax communities involve larger forest which get rid of marshlands etc which are the habitat of many species so conservation can involve mowing the grass so no trees grow or allowing cows to graze there so no trees grow
What is conservation?
- The protection and management of an ecosystem
What conflicts can be had between conservation and human needs?
- Some farming is quite aggressive and leaves the land bare but it is some people’s way of life and human business demand requires a large income of resources
How can business be made better for conservation?
- Teach sustainable farming
- Plants conserved in seed banks
- Fishing quotas added
- Protected areas such as national parks
- Endangered species bred in captivity to increase numbers
