6.3.2 Populations and Sustainability Flashcards
1
Q
How do abiotic factors vary population size?
A
- when abiotic conditions are ideal for a species, organisms can grow fast and reproduce successfully
- when abiotic conditions aren’t ideal, organisms can’t grow as fast or reproduce successfully
2
Q
What three types of biotic factor vary population size?
A
- interspecific competition: competition between different species
- intraspecific competition: competition within species
- predation
3
Q
Describe how interspecific competition affects population size
A
- interspecific competition is when organism of different species compete with each other for the same resources e.g. red and grey squirrels
- this may mean that reproduces available to both populations are reduced.
- this means their populations will be limited by a lower amount fo food so they’ll have less energy for growth and reproduction
- so population sizes will be lower for both species
- it can also affect distribution of species
- one may be better adapted to its surroundings and the less well adapted species would be out-competed
4
Q
Describe how intraspecific competition affects population size
A
- the population of a species increases when resources are plentiful
- as the population increases, there’ll be more organisms competing for the same amount of space and food
- eventually, reproduces such as food and space become limiting as there isn’t enough for all
- populations begin to decline
- a smaller population means there’s less competition for space and food, which is better for growth and reproduction, so population grows again
- the maximum stable population sizes of a species that an ecosystem can support is called the carrying capacity
5
Q
Describe how predation can affect population size
A
- population controlled by negative feedback
- as the prey population increases, there’s more food for predators, so the predators population grows
- as the predator population increases, more prey is eaten, so prey population begins to fall
- prey population restored to a more stable size
- so there’s less food for predators, so their population decreases
6
Q
Describe a population growth graph
A
- lag phase: there may only be a few individuals, still adapting to their habitat
- rate of reproduction is low and growth in population is slow
- log phase: resources are plentiful and conditions are good. reproduction happens quickly, with rate of reproduction exceeding mortality. population increases rapidly
- stationary phase: population size has levelled out at carrying capacity. habitat can no longer support larger population. rate of reproduction and mortality are equal
7
Q
What is conservation?
A
- conservation is the protection and management of ecosystems so that the natural resources in them can be used without them running out
- so that natural resources can be still available for future generations
- it is a dynamic process: adapted to constant changes q
8
Q
Why is conservation important?
A
Economic:
- ecosystems provide resources for humans e.g. rainsforests contain species that provide drugs, clothes and food
- these resources are economically important because they’re traded on a local and global scale
- if they aren’t conserved, resources we use now will be lost and there will be less trade in the future
Social:
- attractor and bring joy to people
- used for activities e..g walking
- future generation won’t be able to use them if destroyed
Ethical:
- It is the right thing to do as it shouldn’t become extinct due to human activity
- we have moral responsibly to conserve ecosystems for future generations so they can enjoy and use them
9
Q
What is preservation?
A
- the protection of ecosystems so they’re kept exactly as they are
- nothing is removed and they are only used for activities that don’t damage them
10
Q
Describe how small-scale timber production can be managed
A
- coppicing provides a sustainable supply of wood
- stem of a deciduous tree is cut close to the ground
- new shoots grow from the cut surface and mature into narrow stems
- pollarding may also occur
- wood is divided into sections and cut one section each year. this is rotational coppicing
- this allows the new stems from the first section to grow larger
- in each section, some trees are left to grow larger without being coppiced. they are standards and supply larger pieces of timber
- rotational coppicing is good for biodiversity as it lets more light in and increases number of diversity of species
11
Q
Describe how large-scale timber production can be managed
A
- clear felling was used
- destroyed habitats on a large scale and reduce soil mineral levels, leaving soil susceptible to erosion
- the soil may run into waterways, polluting them
- now rarely practised
- ant tree harvested is replaced by another tree
- selective cutting is used to remove only the largest, more valuable trees, leaving the habitat broadly unaffected
- control pest and pathogens
- only plant tree species that will grow well
- position trees an optimal distance apart, decreasing competition for light
12
Q
How can fish stocks be managed
A
Using fishing quotas:
- fishing quotas limit the amount of certain fish species that fishermen can catch
- scientists study different species and decide how big their populations need to be to maintain their number
- then they decide how much fish is safe to catch
- international agreements such as Common Fisheries Policy in EU state the amount of fish each country can stake
- these quotes help conserve dish by reducing numbers caught and killed, so populations don’t reduce so much they are extinct
- however, fish of wrong species are thrown back dead or dying but new rules are being made
COntrolling Mesh size of Nets:
- different limits of mesh size of the fish net, depending on whats being fished
- to reduce number of unwanted or discarded dish that are accidentally caught
- bigger size helps younger fish slip through to breed
- it is hard to determine exact fish net size and two nets could be used one inside the other to reduce net size.
13
Q
Explain the conservation and human needs in the Terai region
A
- in the south of Nepal, the Terai region, is made up of marshy grasslands, savannah and forests
- it is densely populated and home to endangered Bengal tiger and one-horned rhino
- many national parks
- under pressure from expansion of agriculture, grazing from farm animals, over-exploitation of forest resources and replacement of traditional agricultural crop varieties with modern ones
- WWF found that rural livelihoods are heavily dependent on forests
- provides local with sustainable source of fuel, animal feed, food etc
- The Terai-arc landscape programme between WWF and Nepalese government focused on conservation of forest landscape
- created forest corridors between national parks for tigers
- counteracted poaches and illegal felling
- forestry work built entrepreneurial skills
- constructed waterholes, monitored endangered species and eradicate invasive species
- tiger populations are said to be growing steadily
14
Q
Explain the conservation and human need of the Maasai Mara
A
- large populations of antelope and large mammals
- high poverty so area is used to attract tourism to help locals, and conserving habitats
- National parks created in 1945
- density of wildlife has dropped 65% over the last 30 years, while density of sheep increased
- partnerships between conservancies and tourism operators have developed for conservation schemes
- said to be successful
- however, land owners must move their livestock out during the tourist season, and forced to settle elsewhere
15
Q
How are the effects of human activities controlled in the Galapagos
A
- has high numbers of native species
- 50% of vertebrate species and 25% of plant species are endangered
Habitat disturbance:
- Population size increase has placed huge demands on water, energy and sanitation services
- more waste and pollution produced, demand for oil increased
- buikding and agriculture has caused destruction of habitats
- Scalesia trees have almost been eradicated on Santa Cruz island
Overexploitation of resources:
- Charles Darwin Research station has a captive breeding programmed to supplement tortoise numbers
- boom in fishing acoustic species has depleted populations
- sea cucumbers decrease has affected the death of 150,000 shark each year
Effects of introduced species:
- alien species have been introduced
- lava lizard and young iguanas
- Giant African Land Snails: detected on Santa Cruz islands
- produce 100-3000 eggs a month, spreading quickly
- consumes at least 500 different plants, threatening native snails and plants
- dog detection used
Management:
- in 1999 charles darwin research station search arriving boats and tourists for foreign species
- 36% of coastal zones have been designated NO-take areas where no extraction of resources is allowed
