Module 6 Section 7: Populations and Sustainability

Question 1

What is population size

Answer 1

Total number of organisms of one species in a habitat

Question 2

Why may a population size fluctuate

Answer 2

Can vary due to abiotic factors
This includes the amount of light, water, space available, temperature of surroundings, chemical composition of surroundings

Due to biotic factors
Interspecific or Intraspecific competition

Question 3

What happens when abiotic factors are ideal for a species

Answer 3

Organisms can grow fast and reproduce successfully
E.g. when temperature is optimum level for growth, mammals don’t have to use up energy to keep warm or cool down so more can be focussed on growth and reproduction

Question 4

What happens when abiotic factors are not ideal for a species

Answer 4

Organisms won’t grow as fast or reproduce as successfully
E.g. a mammal may have to spend more energy cooling down or heating up so less energy can be available for growth or reproduction

Question 5

What is Interspecific competition

Answer 5

When organisms of different species compete with eachother for the same resources
E.g. red and grey squirrels compete for same food sources and habitats in UK

Question 6

How may Interspecific competition affect resources available for both competing species

Answer 6

Resources available to both populations are reduced
This can mean both populations will be limited by a lower amount of these resources (e.g. food)
They will have less energy available for growth and reproduction so populations sizes will be lower for both species

Question 7

How may Interspecific competition affect the distribution of species

Answer 7

If two species are competing but one is better adapted to the surroundings than the other, the less well adapted will be out-competed
This means it won’t be able to exist alongside the better adapted species
Known as competitive exclusion principle: if two species are competing for limited resources, the one that uses the resources more effectively will ultimately eliminate the other

Question 8

What is Intraspecific competition

Answer 8

When organisms of the same species compete with each other for the same resources

Question 9

Process of how a population of a species can change with Intraspecific competition

Answer 9

1) The population of a species increase when resources are plentiful
As the population increases, there’ll be more organisms competing for the same amount of space and food

2) Eventually, resources (food and space) become limiting and there isn’t enough for all the organisms
The population then begins to decline

3) A smaller population means that there’s less competition for space and food, which is better for growth and reproduction
Population starts to grow again

4) The maximum stable population size of a species that an ecosystem can support is called the carrying capacity

Cycle of events then repeats again

Question 10

Label the graph

Answer 10

Question 11

What is the lag phase

Answer 11

Lag phase:
Population increases less rapidly
Small numbers of individuals that are initially present reproduce to increase the total population
Birth rate higher than death rate so population increases in size

Question 12

What is the log phase

Answer 12

Log phase:
Exponential growth
Number of breeding individuals increases and the total population multiplies exponentially
No constraints act to limit the population growth

Question 13

What is a stationary phase

Answer 13

Stationary phase:
Further growth is prevented by external constraints
Population size fluctuates but remains relatively stable
Birth rates and death rates approximately equal
Fluctuation is caused by slight differences in limiting factors

Question 14

What are limiting factors

Answer 14

Limiting factors
These stop the population from growing exponentially after log phase
Can prevent further growth or cause a decline
E.g: competition for resources, build up of toxic by-products of metabolism or disease
Can be either abiotic (temperature, light, pH, water or oxygen availability and humidity) or biotic factors (predators, disease, competition)

Question 15

Explain the predator prey relationship

Answer 15

Increase in prey population provides more food to predators
Predators are allowed to survive and reproduce
This results in an increase in the predator population

Increase predator population eats more prey
Causes a decline in prey population
Death rate of prey population is greater than birth rate

Reduced prey population can no longer support large predator population
Intraspecific competition for food increases, resulting in a decrease in the size of the predator population

Reduced predator numbers result in less of the prey population being killed
More prey organisms survive and reproduce
This increases the prey population and the cycle begins before

Question 16

What is conservation

Answer 16

The protection and management of ecosystems so the natural resources in them can be used without them running out
So the resources can be available for future generations

Question 17

What is preservation

Answer 17

The protection of ecosystems so they’re kept exactly as they are.
Nothing is removed from a preserved ecosystem and they’re only used for activities that don’t damage them.

Question 18

How is conservation a dynamic process

Answer 18

Conservation must be adapted to the constant changes that occur within ecosystems
(These changes can occur naturally and from humans)

Question 19

What does conservation involve

Answer 19

Management of ecosystems:
Controlling how resources are used and replaced
Reclamation of ecosystems:
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.

Question 20

What are the main categories for why conservation is important

Answer 20

Economic reasons
Social reasons
Ethical reasons

Question 21

Why is conservation important for economic reasons

Answer 21

Ecosystems provide resources for lots of things that humans need
E.g. rainforests contain species that provide things like drugs, clothes and food.
These are 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.

Question 22

Why is conservation important for social reasons

Answer 22

Many ecosystems bring joy to lots of people
They’re attractive to look at and people use them for activities
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.

Question 23

Why is conservation important for ethical reasons

Answer 23

Some people think we should conserve ecosystems simply because it’s the right thing to do
This means that animals shouldn’t go extinct due to human activity

Some people think we have a moral responsibility to conserve ecosystems for future generations, so they can enjoy and use them.

Question 24

What is sustainable management of ecosystems

Answer 24

It means that the ecosystem is managed in a way that means enough resources are taken to meet needs of people today but not to reduce the ability of people in the future to meet their own needs

Question 25

Name the techniques in which woodlands are managed sustainably

Answer 25

For every tree that’s cut down for timber, a new one is planted in its place
Trees cleared in strips or patches so woodland grows back more quickly that it would if the woodland had been cleared in larger, open areas

The cleared strips or patches aren’t too large or exposed otherwise soil erosion can occur on the bare ground
This can restrict the growth of newly planted trees

Timber can be harvested by coppicing which allows trees to grow back without planting new ones

Native tree species tend to be planted over non-native ones
This is better for biodiversity as existing organisms (plants, fungi, animals) already has established links to these trees
This helps them thrive

Planted trees attached to posts to provide support and grown in plastic tubes to stop herbivory so they can grow to adulthood

Trees aren’t planted too close together so they aren’t competing for space or resources, so they’re more likely to survive

Question 26

Characteristics of small scale timber production

Answer 26

Coppicing used where tree trunk cut close to the ground and new shoots grow from the surface
Shoots then cut and more produced

Rotational coppicing usually takes place

Pollarding can be used where trunk is cut up higher so animals can’t eat the shoots

Question 27

Process of rotational coppicing

Answer 27

Woodland is divided into sections and trees are only cut in particular section until all have been coppiced
Coppicing then begins in another area which allows time for the newly coppiced trees to grow
Process repeats until you reach the trees that were first coppiced which have now grown to mature sized trees

This maintains biodiversity as the trees never grow enough to block out light
Succession cannot occur so more species survive

Question 28

Characteristics of large scale timber production

Answer 28

Where larger areas of forest are felled
Felled trees are destroyed and will not regrow

Question 29

Disadvantages of large scale timber production

Answer 29

Habitats are destroyed, soil minerals reduced, base soil left is susceptible to erosion
Trees not there to bind soil together
Trees not there to remove water from soil
Trees can’t maintain nutrient levels through their role in carbon and nitrogen cycles

Question 30

Why do we need to fish more sustainably

Answer 30

Overfishing has been causing fish stocks to decline recently
Means that there is less fish to eat and the ocean’s food chain are affected as trophic levels can disappear altogether
We need to maintain fish stocks at a level where fish continue to breed

Question 31

What are the ways in which fishing is managed in a sustainable way

Answer 31

Fishing quotas
Controlling mesh size of nets
Allowing commercial fishing at certain times of the year
Introduction of fish farming to prevent loss of wild species

Question 32

What are fishing quotas

Answer 32

Limits to the amount of certain fish species that fisherman are allowed to catch
These are supposed to help conserve fish species by reducing the numbers that are caught and killed
This means that populations aren’t reduced too much and the species aren’t at risk from becoming extinct

Question 33

How are fishing quotas made

Answer 33

Scientists study different species and decide how big their populations need to be for them to maintain their numbers.
Then they decide how many it’s safe for fishermen to take without reducing the population too much.

International agreements are made that state the amount of fish each country can take, and where they’re allowed to take them from.
E.g. the Common Fisheries Policy in the EU

Question 34

Problems with using fishing quotas

Answer 34

Fish of wrong size of species are caught then thrown back into the sea while they are dead or dying as fishermen are restricted from bringing them ashore
New rules for the Common Fisheries Policy are banning the discarding of fish like this and the whole catch will have to be brought ashore to be counted against the quota.

Question 35

What is the controlling of mesh size of nets

Answer 35

Mesh size limit can change depending on what’s being caught
This is to reduce the number of unwanted and discarded fish that are accidentally caught
Using a bigger mesh size will let the unwanted species escape
Means that younger fish will slip through the net, allowing them to reach breeding age

Question 36

Problems with controlling mesh size of nets

Answer 36

Can be difficult to determine exactly how big the mesh size should be in areas where several different fish species are fished for at the same time.
Two nets, each of which meets regulations, could be used one inside the other - effectively reducing the reported mesh size

Question 37

Conservation and preservation of Terai Arc be balanced with human needs

Answer 37

Area of forest and grassland between Nepal India
Home to a variety of plants and animals are found there (endangered species like Bengal Tiger and Asian elephant)

7 million people also live in this area
Area of the forest are being destroyed to make way for more housing and other development- this destruction of habitat brings humans and animals into closer contact and increases the contact between the two
E.g. elephants eat and trample crops and tigers can kill livestock which increases the likelihood of these animals being shot and killed

Conservation charity (WWF) has worked with local people to help balance their needs with with conserving the forest and its wildlife
E.g. charity provided people with solar cookers and biogas generators, so they don’t use wood from forest
Farmers are encouraged to plant mint hedges around their crops to keep animals away

Question 38

Conservation and preservation of Masai Mara be balanced with human needs

Answer 38

Large area of savannah which is home to large populations of wildebeest, zebra, lions and cheetah
Named after Maasai people

Maasai people earn a living by raising livestock such as cattle
This can bring them into conflict with conservationists (e.g. overgrazing by livestock can destroy grassland for wildlife)

Conservation trusts are working with the Maasai people to help them make money from their land through conservation and ecotourism projects rather than farming, and to farm in a sustainable way
This means that the economic needs of the Maasai people are met while allowing the area to be conserved

Question 39

Conservation and preservation of UK peat bogs be balanced with human needs

Answer 39

Upland UK areas are home to peat bogs
Peat bogs store water and CO2 and are home to lots of different plants and animals (mosses here can help the pest bog form by retaining water

Farmers use the peat bogs to graze sheep and deer
Can lead to conflict with conservationists because overgrazing causes loss of moss species, soil compaction (increases surface runoff down sheep paths, taking sediment with it) and erosion of the peat bogs

Recent government-funded programmes (Environmental Stewardship Scheme) have given farmers money to use the peat bogs in a sustainable way
E.g. to carry out measures to reduce water runoff, to lower the number of livestock that use the peat bogs, and to remove livestock over winter

Question 40

Disadvantages of fish farming

Answer 40

Fish sewage building up on seabed below the nets

Escape of non native fish:
New diseases
Invasive towards food web (new predator)
Habitat disruption

New pathogens and parasites in an ecosystem that hasn’t been exposed

Management of predators

Question 41

What is the ecological context of the Galápagos Islands

Answer 41

Many rare species of animals and plants have evolved there that can’t be found elsewhere.
E.g. Galapagos giant tortoise
Used for the development of the theory of evolution

Question 42

Effects of human activities on the Galápagos Islands

Answer 42

Non-native animals introduced to the islands by humans can prey on some native species.
This has caused a decrease in the populations of native species.
E.g. non-native dogs, cats and black rats eat young giant tortoises and Galapagos land iguanas.
Goats have eaten much of the plant life on some of the islands.

Non-native plants have also been introduced to the islands.
These compete with native plant species, causing a decrease in their populations.
E.g. quinine trees are taller than some native plants so they block out light to the native plants, which then struggle to survive.

Question 43

Methods of control of ecosystems for Galápagos Islands

Answer 43

Eradication programmes have removed wild goats from some of the smaller islands and wild dogs from the largest island.
Quinine trees are kept in check using chemical herbicides and by uprooting young trees.

When people visit the Galapagos National Park they are expected to follow a list of rules
This includes not bringing any live plants or animals onto the islands, or moving them between the islands.
People are also only allowed to visit the Galapagos National Park in the company of a licensed guide.

Question 44

Ecological context of Antarctica

Answer 44

Antarctica is the world’s southernmost continent.
It has a unique icy landscape with plants and animals that have adapted to its harsh conditions.
For at least 200 years it has attracted visitors
E.g. research scientists and tourists.

Question 45

Effects of human activities in Antarctica

Answer 45

Visitors to Antarctica have caused pollution in the past by dumping sewage into the sea and leaving rubbish.
Shipping accidents have lead to oil spills, which severely affect wildlife.
Hunting, whaling and fishing have all reduced wildlife populations in the area.

Question 46

Methods of control of ecosystems in Antarctica

Answer 46

All waste apart from food waste and sewage must be taken away by ship for disposal in other countries.
Many research stations now treat their sewage before releasing it, to reduce its effects on the environment.

Ships that use thick oil as a fuel are now banned from Antarctic waters
This is because heavy oil spills are likely to cause more damage and be harder to clean up than spills of lighter fuels.

There are tourist restrictions
E.g. tourists are only allowed on land at certain locations for a few hours.
Hunting and whaling have been banned for some time now, although fishing still continues.

Question 47

Ecological context of Snowdonia

Answer 47

National park in north wales
Contains lakes, and fast flowing rivers and wide tracts of ancient woodland
Home to a number of different mammals and birds
Home to diverse range of plants
E.g. Snowdon Lily

Question 48

Ecological context of the Lake District

Answer 48

Contains regions of moorland and fell
Dales and fringes of lakes provide a rich variety of habitats
E.g. areas of ancient woodland
Home to wide range of wildlife and plants that have adapted specially to this environment
E.g. Golden eagle and dwarf willow

Question 49

Effects of human activities of Lake District and snowdonia

Answer 49

Many of the visitors to the Lake District go walking on the region’s footpaths.
This leads to the erosion of the footpaths and the loss of soil from hillsides.
Soil that ends up in waterways and lanes can disturb the pH of the water, causing knock-on effects for wildlife.

As the paths become harder to walk on, people can start to trample and destroy the sensitive vegetation either side of the paths

A lot of rain falls in the Snowdonia hills, which leads to the erosion of the paths.
Walkers often trample the surrounding vegetation as they try to walk around the floods

Question 50

Methods of control of ecosystems in Snowdonia and Lake District

Answer 50

In the Lake District, conservation charities and the Lake District National Park Authority attempt to carry out regular repair and maintenance work on the paths and encourage the regrowth of damaged vegetation.

Walkers are also educated about the importance of sticking to the paths and not taking short cuts, as these increase erosion.

In Snowdonia, volunteers have dug drains next to the paths to prevent them from flooding.

Question 51

What is the carrying capacity

Answer 51

Maximum population size that an environment can support is known as its carrying capacity and population remains equal as the number of births and deaths are the same