Populations and sampling Flashcards
What is population size
The total number of organisms of one species in a habitat
Why does the population size of any species varies
Due to abiotic factors
What is interspecific competition
When organisms of different species compete with each other for the the same resources
What causes inter and intraspecific competition
Biotic factors
What are the repercussions of interspecific competition
The resources avaliable to both populations are reduced. So both populations will be limited by a lower amount of food and have less energy for growth and reproduction.
It can also affect the distribution of species as if two species are competing and one is out-competed it likely won’t survive alongside the more adapted species.
What is intraspecific competition
When organisms of the same species compete with each other for the same resources
How does the number of species fluctuate during intraspecific competition
1) The population of a species increases when resources are plentiful
2) Eventually resources such as food and space become limiting and the population declines
3) A smaller population means there is less competition for space and food so is better for growth and reproduction. And the population grows again
What is the carrying capacity
The maximum stable population size of a species that an ecosystem can support
What is predation
Where an organism kills and eats another organism
What is negative feedback
It restores systems to their original level and is a mechanism in which the output of a process leads to a decrease in the output.
How does negative feedback control population size
1) As prey population increases there is more food for predators, so predator population grows
2) As the predator population increases, more prey is eaten so the prey population begins to fall
3) There is then less food for the predators so their population decreases
How do limiting factors affect population size
They determine the carrying capacity of an ecosystem, therefore stopping the population size increasing
Define conservation
The protection and management of ecosystems so that natural resources in them can be used without running out
What economic benefit does conservation have
Ecosystems provide resources for humans such as drugs, clothes and food. They are then traded globally and locally so if not conserved trade will reduce
What social benefit does conservation have
Ecosystems bring joy to people as they are attractive to look at and are used for activities.
What ethical benefits does conservation have
1) Some people think it is the right thing to do as the organisms should have a right to exist
2) We have a moral responsibility to conserve ecosystems for future generations
What is coppicing
It involves felling trees at their base to create a ‘stool’ where new shoots will grow
What is planted in preference when sustaining a woodland
Native tree species as they are better for biodiversity
What is clear felling
All the trees in an area are cut down
What is pollarding
A type of coppicing where the trees are cut higher up
What is selective logging
The removal of selected trees within a forest based on criteria such as diameter, height, or species.
Why are fish stocks declining
Overfishing
How can fishing happen in a sustainable way
Using fishing quotas - limits the amount fisherman are able to catch
Controlling mesh size of net - bigger mesh size stops the unwanted fish such as shrimps being caught as well. It also means younger fish can slip through and then reach breeding age.
Disadvantage of fishing quotas
Fish of the wrong species or size accidently get caught and then put back dead or dying
Disadvantage of controlling mesh size of nets
It can be difficult to determine how big the mesh size should be.
Also some people use two approved nets one inside the other reducing the reported net size
