4: Populations and Succession Flashcards
What is an ecosystem?
all the interacting biotic and abiotic features of a specific area
What is a population?
a group of organisms of one species in a habitat
What is a community?
all the populations of different organisms living in a particular place at the same time
What is a habitat?
a place where a community of organisms lives
What is a niche?
all the abiotic and biotic factors required for an organism to survive
When deciding on how many quadrats to lay, how would you know when to stop sampling?
when the running mean is no longer changing
Why is it important for sampling to be random?
to avoid bias
What is the mark-release-recapture formula?
estimated population size = (number in 1st sample x number in 2nd sample) / number of marked
What assumptions does the mark-release-recapture technique rely on?
- no immigration or emmigration
- no births or deaths
- the marked individuals are distributed evenly among the population
- the marker does not make the individual more susceptible to predation
- the marker does not rub off
What is an abiotic factor? Give examples.
a non-living factor
E.g. - temperature, light intensity, pH, water/humidity
What is a biotic factor?
a living factor
E.g. - competition, predation
What is intraspecific competition?
Competition between individuals of the same species for resources such as food and water
Describe the effect of the predator-prey relationship on population size
- predators eat their prey, prey pop reduces
- with fewer prey available the predators are in greater competition with each other
- the predator population is reduced as some individuals are unable to obtain enough prey to survive
- With fewer predators, fewer prey are eaten
- The prey population increases
- With more prey now available as food, the predator population in turn increases
Factors affecting death rate
age profile (more elderly = higher death rate), food supply (good diet reduces death rate), access to clean water, good sanitation, medical care quality, natural disasters, war
Describe the process of succession
- colonisation by pioneer species
- these species change the environment by forming humus/soil containing organic matter and nutrients
- this enables other species to colonise
- environment becomes less and less hostile
- more and more species can colonise which increases biodiversity
- the stability of the environment increases until a climax community is reached
What are the features of an area undergoing succession?
- environment becomes less hostile
- number and variety and habitats and food souces increases
- more complex food webs
- increased biodiversity
- more niches
- increased biomass
Why does soil nitrate concentration increases durning succession?
Increase in dead organisms/humus/decomposition
Leading to nitrification
And nitrogen fixation
Pioneer species seeds are often adapted to germinate in fluctuating temperatures.Why is this an advantage?
Lots of exposed soil at start of succession
Bare soil temperatures fluctuate
What is secondary succession?
This 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
What is the climax community called when succession is stopped artificially?
Plagioclimax
Describe how mowing a lawn prevents succession
A regularly mown grassy field won’t develop shrubs and trees, even if the climate of the ecosystem could support them. Lawn mower cuts off growing parts of woody plants so plants can’t establish themselves. The longer the intervals between mowing, the further succession can progress and the more diversity increases. But with more frequent mooring, succession can’t progress and diversity with be lower - only the grasses can survive being mowed
What is conservation?
Describe two methods of conservation?
Sometimes involves preventing succession in order to preserve an ecosystem in its current seral stage
Animals allowed to graze
Managed fires are lit, leads to secondary succession
Why is conservation important?
Species are resources that may be useful in the future
Ethical issues, species have a right to exist
Attractive to look at, bring joy to people
Helps prevent climate change e.g. Prevents trees being burnt
Prevents the disruption of food chains
5 ways different species can be conserved
Seed banks for plants Fishing quotas for fish Captive breeding programmes for animals Relocation - any organism Conserve habitats using protected areas
