Populations and sustainability Flashcards
what is meant by population?
a population is al the organisms of one species in a habitat
what is meant by population size?
population size is the total number of organisms of one species in a habitat. this number changes over time because of the effect of various factors
what are some examples of abiotic factors that effect the population size?
- the amount o flight
- water
- space available-the temperature of their surroundings
- the chemical composition of their surroundings
what happens when abiotic factors are ideal for a species?
organisms can grow fast and reproduce successfully.
what does it mean for mammals to have their ideal temp for metabolic reactions to take place?
- they don’t have to use up as much energy maintaining their boy temp.
- this means more energy can be used for growth and reproduction, so their population size will increase.
what are some examples of biotic factors that effect the population size?
- interspecific competition
- intraspecific competition
- predation
what is meant by interspecific competition?
interspecific competition is when organisms of different species compete with each other for the same resources.
what does interspecific competition lead to in terms of with food?
- this can mean that the resources available to both populations are reduced
- e.g. if they share the same source of food, there will be less available to both of them.
- this means both populations will be limited by a lower amount of food.
- they’ll have less energy for growth and reproduction
- so the population sizes will be lower for both species
how does interspecific competition affect the distribution of species?
- interspecific competition can also affect the distribution of species.
- if 2 species are competing but 1 is better adapted to its surroundings than the other
- the less well adapted species is likely to be out- competed- it won’t be able to exist alongside the better adapted species
how did the introduction of grey squirrels lead to interspecific competition?
- grey squirrels were introduced to the UK
- they now compete with the native red squirrels for the same food sources and habitats
- as they share the same source of food, there is less available to both of them.
- so in areas where both red and grey squirrels live, both populations are smaller than they would be if there was inly 1 species there
- since the introduction of the grey squirrel to the UK, the native red squirrel has disappeared from large areas.
- they grey squirrel has a better chance of survival because it’s larger and can store more fat over winter
- it can also eat a wider range of food than the red squirrel.
what is meant by intraspecific competition?
intraspecific competition is when organisms of the same species compete with each other for the same resources.
what can intraspecific competition lead to and why?
- it can cause a cyclical change in population size, where the population grows, shrinks, grows again and so on.
- this is because the population of a species increases when the resources are plentiful.
- As the population increases, there’ll be more organisms competing for the same amount of space and food.
- eventually resources such as food ans space become limiting- there isn’t enough for all the organisms.
- the population then begins to decline.
- a smaller population then means that there is less competition fro space and food, which is better for growth and reproduction- so the population starts to grow again.
what is meant by carrying capacity?
the maximum stable population size of a species that an ecosystem can support is called the carrying capacity.
what is meant by predation?
predation is when an organism (he predator) kills and eats another organism (the prey), e.g. lions kill and eat (predate on) buffalo.
why is the population of predators and prey interlinked?
-a s the population of 1 changes, it causes the other population to change through negative feedback
what is meant by negative feedback?
negative feedback i s when a a system reacts to a change in a way that pushes it back toward a stable state
what happens in a predator-prey system as the prey population increases?
-there’s more food for predators, so the predator population grows.
what happens in a predator-prey system as the predator population increases?
- As the predator population increases, more prey is eaten so the prey population then begins to all - this is a negative feedback effect that restores the prey population to a more stable size.
- this means there’s less food for the predators, so their population decreases (another negative feedback effect), and so on.
what are limiting factors and what do they do?
limiting factors stop the population size of a species increasing- they determine the carrying capacity of an ecosystem.
-Limiting factors can be biotic or abiotic.
give an example of an abiotic limiting factor
the amount of shelter in an ecosystem limits the population size of a species as there’s only enough shelter for a certain number of individuals.
give an example of an biotic limiting factor
Interspecific competition limits the population size of a species because the amount of resources available to a species is reduced.
what is meant by conservation?
+ e.g.
conservation is the protection and management of ecosystems so that the natural resources in them van be used without them running out.
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e.g. using rainforests for timber without any species becoming extinct and without any habit being destroyed. This means the natural resources will still be available or future generations.
how is conservation a dynamic process?
conservation is a dynamic process- conservation methods need to be adapted to the constant changes (caused naturally and by humans) that occur within ecosystems. It involves the management of ecosystems- controlling how resources are used and replaced.
why is it believed that conservation can also involve reclamation?
restoring ecosystems that have been damaged or destroyed so they can be used again, e.g. restoring forests that have been cut down so they can be used again
what are the 4 main reasons why conservation is important?
- economic reasons
- social reasons
- ethical reasons
- ecological reasons
why is conservation important for economic reasons?
- ecosystems provide resources for lots of things that humans need, e.g. rainforests contain species that provide things like drugs, clothes and food.
- These resources re economically important because they’re traded on a local and global scale.
- If the ecosystems aren’t conserved, the resources that we use now will be lost, so there will be less trade in the future.
why is conservation important for social reasons?
- many ecosystems bring joy to lots of people because they’re attractive ti look at and people use them for activities e.g. birdwatching and walking.
- The species and habitats in the ecosystems may be lost if they aren’t conserved, so future generations won’t be able to use and enjoy them.
why is conservation important for ethical reasons?
- some people think we should conserve ecosystems simply because its the ‘right’ thing to do - e.g. most people think organisms have the right to exist, so they shouldn’t become extinct as a result of human activity.
- Some people think we have a moral responsibility to conserve ecosystems for future generation, so they can enjoy and use them.
why is conservation important for ecological reaons?
- conserving species and habitats can help prevent climate change. E.g.- when trees are burnt Co2 is released into the atmosphere, which contributes to global warming.
- if the trees are conserved, this doesn’t happen.
- conserving species and habitats also help prevent the disruption of food chains.
- disruption of food chains can have knock-on effects on other organisms, e.g. – some species of bear feed on salmon, which feed on herring- if the number of herring decreases it can affect both the salmon and the bear population.
what is meant by preervation?
preservation is different from conservation- it’s the protection of ecosystems so they’re kept exactly as the are. Nothing is removed from a preserved ecosystem and they’re only used for activities that don’t damage them.
how is Antarctica a preserved ecosystem?
Antarctica is a preserved ecosystem because it’s protected from exploitation by humans- it’s only used for limited tourism and scientific research, not mining or other industrial activities.
how can temperate woodland be managed in a sustainable way?
for every tree that’s cut down for timber, a new one is planted in its place. The woodland should never become depleted.
what are 6 things that need to be done to ensure that the careful cutting down and replanting trees is done successfully?
1-trees are cleared in strips or patches- woodland grows back more quickly in small areas between bits of existing woodland than it does in larger, open areas
2-the cleared strips or paths aren’t too large or exposed- lots of soil erosion can occur on large areas of bare ground. If the soil is eroded, newly planted trees won’t be able to grow.
3-timber is sometimes harvested by coppicing- cutting down trees in a way that lets them grow back. this means new trees don’t need to be planted.
4-Native tree species tend to planted in preference to non- native species. this is better for biodiversity because native species have long- established interactions with other native species (e.g. plants, fungi, animals), so their presence should help species thrive in an area. Also some species might not adapt to the presence of non- native tree species.
5- planted trees are attached to posts to provide support, are grown in plastic tubes to stop being eaten by grazing animals - this makes it more likely the trees will survive to become mature adults.
6-trees aren’t planted too close together- this means the trees aren’t competing with each other for space or resources, so they’re more likely to survive.
what is the consequence of overfishing?
-overfishing has led to a decline in fish stocks in many parts of the world. This may lead to some species of fish disappearing altogether in some areas, and has the potential to severely disrupt ocean food chains.
why is fish so important?
- fish is an important part of many people’s diets and fishing provides employment for many people, so we need to maintain fish stocks at a level where the fish continue to breed.
- This is sustainable food production- having enough food without using resources faster than they renew.
what are the different ways of managing fish stocks?
- using fishing quotas
- making regulations on mesh sizes
what are fishing quotas and what is their aim?
- fishing quotas are limits to he amount of certain fish species that fishermen are allowed to catch.
- Fishing quotas are supposed to help to conserve fish species by reducing too much and the species aren’t at risk from becoming extinct.