SB9 - Ecosystems and Material Cycles

Question 1

What is an ecosystem?

Answer 1

All the organisms and the environment in which they live (combination of all biotic and abiotic factors).

Question 2

What is a community?

Answer 2

All the organisms that live and interact in an ecosystem form a community (biotic factors).

Question 3

What is a population?

Answer 3

A number of the same species within a community.

Question 4

What is interdependence?

Answer 4

When different species are reliant on each other for survival

Question 5

What is a habitat?

Answer 5

An area within an ecosystem in which organisms live. It includes the other organisms that affect the population and the local environment.

Question 6

What is abundance?

Answer 6

A measure of how common something is in an area, such as it’s population size.

Question 7

What is a quadrat?

Answer 7

A wire frame with squares in it which can be placed in a habitat to estimate the population of a species in that habitat.

Question 8

How can population size be estimated using quadrats?

Answer 8

Quadrats are placed randomly in the area and the number of individuals in each quadrat is counted. The population size is estimated using the equation

Population size = number of organisms in all quadrats x total size of area where organism lives / total area of quadrats

Question 9

What is a food web?

Answer 9

A diagram which shows the feeding relationships between the organisms in a community.

Question 10

What is biomass?

Answer 10

The mass of tissues of an organism.

Question 11

What are tropic levels?

Answer 11

Feeding levels of a food chain. The producer is one trophies level, then the primary consumer is another, then the secondary consumer is another etc.

Question 12

How is energy lost between tropic levels?

Answer 12

• some energy is transferred to the surroundings by heating during metabolic processes
• some energy is excreted in faeces and urine
• whenever the animal moves, it uses energy

Question 13

How can you calculate the efficiency of energy transfer between organisms?

Answer 13

Energy transferred to biomass / total energy supplied to organism

Question 14

What is a pyramid of biomass?

Answer 14

A diagram which shows the biomass of all the organisms at each tropic level in an ecosystem.

Question 15

Why is a pyramid of biomass generally wider at the bottom than at the top?

Answer 15

Energy is transferred to the environment at each tropic level. With less energy available, less biomass can be produced.

Question 16

Why is there a limit to the length of food chains?

Answer 16

The energy stored in the biomass of the top trophic level is too little to support another level

Question 17

What is the distribution of organisms?

Answer 17

Where they are found in an ecosystem

Question 18

What are abiotic factors?

Answer 18

Non-living factors which affect the distribution of organisms.

Question 19

Give some examples of abiotic factors.

Answer 19

Temperature, rainfall, humidity, soil pH, wind, light intensity, water availability

Question 20

What is a belt transect?

Answer 20

When quadrats are placed along a line in a habitat, and the abundance of the organisms is measured as well as the abiotic factors in each quadrat position.

Question 21

What are belt transects used to measure?

Answer 21

The effect of abiotic factors on the distribution of organisms. It can also show which abiotic factor has the greatest effect on distribution is multiple factors are being investigated.

Question 22

Give an example of how a natural abiotic factor would affect a community.

Answer 22

Organisms are adapted to living in an environment with a particular temperature (e.g. polar bears are adapted to living in cold regions)? If there is a long-term rise or fall in temperature, this will affect the distribution of the species, which will in turn affect that species’ predators and so on.

Question 23

How can abiotic factors caused by humans influence organisms?

Answer 23

Many human activities release pollutants, which can poison organisms or cause harm to organisms in other ways (such as plastics being eaten by fish and other organisms).

Question 24

Core practical - quadrats and transects

Answer 24

• peg out a long tape measure on the ground, starting where there is no shade and ending in heavy shade. This is the transect line
• you will need to make measurements at regular intervals along the transect line. Decide on your intervals, which may depend on how long the line is and how much time you have to complete the investigation
• place the top left-hand corner of the quadrat at a measurement point on the transect line
• measure the abiotic factors at that point and record them
• record the abundance of your selected plants in the quadrat
• repeat this method at different measurement points along the transect

Question 25

Give an example of how biotic factors can affect an ecosystem.

Answer 25

In Yellowstone National Park, wolves has been the top predator until 1926, when they became extinct due to hunting. After that, the number of elk increased rapidly. Their huge numbers caused overgrazing if tree species, which left little food for other herbivores, including beavers. The number of coyotes also increased due to lack of competition for young elk.in 1995, grey wolves were reintroduced to Yellowstone, increasing the predation of elk. This led to an increase in beaver numbers, which created pools and muddy areas (as beavers build dams). These new habitats allowed more species to grow, increasing the biodiversity.

Question 26

What is biodiversity?

Answer 26

The number of different species in an area.

Question 27

What is a predator-prey cycle?

Answer 27

When the numbers of a predator and its prey are closely correlated (as numbers of one increase, numbers of the other increase and vice versa).

Question 28

What is an indicator species?

Answer 28

The presence or absence of a particular species form an area can give information about the level of pollution in that area.

Question 29

How is lichen an indicator species?

Answer 29

Different species of lichen are different levels of resistant to pollution, meaning the type of lichen present on a particular area can indicate the pollution level in that area.

Question 30

How is blackspot fungus an indicator species?

Answer 30

Blackspot fungus is a pathogen of roses. The fungus cannot grow well where there is a lot of sulphur pollution, so roses in cities rarely suffer from blackspot.

Question 31

What are some causes of water pollution?

Answer 31

• fertilisers
• sewage
• poisonous substances released by factories (such as mercury or detergents)

Question 32

How do different indicator species indicate water pollution levels.

Answer 32

Stonefly nymph dragonfly nymph freshwater shrimp water louse bloodworm sludgeworm

—————> increasing pollution levels

Question 33

What is parasitism?

Answer 33

A feeding relationship where one organism (the parasite) benefits by feeding off a host organism, causing harm to the host.

Question 34

What are some examples of parasites?

Answer 34

Tapeworms, lice, gordian worm, ticks, roundworms, leeches, fleas

Question 35

What is a mutualistic relationship?

Answer 35

Where multiple organisms live in the same habitat and both benefit from a relationship with the other.

Question 36

Give an example of a mutualistic relationship.

Answer 36

Many flowers depend on insects for pollination. The flower benefits by being able to produce fertilised egg cells, and the insect benefits by collecting nectar or pollen from the flower, which it uses for food.

Question 37

What is fish farming?

Answer 37

When lots of fish are bred in a small space to produce more fish to meet global demand.

Question 38

What are some disadvantages of fish farming?

Answer 38

Fish farming causes the changing of the conditions for native species, for example, due to waste and uneaten food sinking to the bottom of the water. Parasites and disease spread easily between the fish in owns, so the fish need to be treated to keep them healthy. However, they can still pass the disease on to native species. Also, this can lead to antibiotic resistance.

Question 39

What are some advantages of fish farming?

Answer 39

It prevents overfishing of fish and so preserves stocks of wild fish. It can also produce enough fish to meet the increasing global demand.

Question 40

What is the difference between an indigenous and a non-indigenous species?

Answer 40

An indigenous species is native to the area, whereas a non-indigenous species is not native to the area, it has been introduced from somewhere else.

Question 41

Why are non-indigenous species introduced?

Answer 41

Sometimes, non-indigenous species are introduced to be grown for food (e.g. soybeans are native to Asia but are grown in many parts of the world for food). Sometimes, non-indigenous species are introduced as a form of biological control (e.g. Australia introduced the cane toad to try and control levels of cane beetles, which were eating the sugar cane crops, however the acne toad soon became an invasive species as they are poisonous and kill native animals).

Question 42

What is eutrophication?

Answer 42

The addition of more nutrients to an ecosystem than it normally has.

Question 43

What causes eutrophication?

Answer 43

When farmers use too much fertiliser, it doesn’t get absorbed by the crops and when it rains, the excess fertiliser enters lakes as runoff. Leaching through the ground can also cause eutrophication.

Question 44

What are the effects of eutrophication on an aquatic ecosystem?

Answer 44

• fertiliser is added to a field and enters a lake as runoff
• high nitrate and phosphate concentrations in the water encourage plants and algae to grow rapidly
• surface plants (algae) grow rapidly and block sunlight, causing the death of the plants below them, which stop producing oxygen by photosynthesis
• decomposing bacteria increase in numbers and and use up more oxygen from the water
• the oxygen concentration of the water decreases
• aquatic animals such as fish die due to lack of oxygen

Question 45

What is conservation?

Answer 45

When an effort is made to protect a rare or endangered species or habitat

Question 46

Why is preserving biodiversity important?

Answer 46

• preserves individual species and communities
• areas with greater biodiversity can recover faster from natural disasters like flooding
• we can use plants and animals as a source of medicines and other products

Question 47

How can biodiversity be preserved?

Answer 47

There are many ways to do this, for example, reforestation projects can create more diverse habitats, which cause a greater variety of species to migrate to the area. Also, reintroducing native species can work, for example the reintroduction of grey wolves to Yellowstone National Park increased biodiversity.

Question 48

What is food security?

Answer 48

Food security is having enough safe and healthy food at all times.

Question 49

How can food security be ensured?

Answer 49

Changing farming practices (e.g. eating farmed rather than wild fish) may help. Also eating more vegetables rather than meat may help. Agricultural inputs (such as fertilisers) can help food security as they increase yields.

Question 50

What is the water cycle?

Answer 50

The process by which water is recycled through organisms and the environment (abiotic and biotic components) to support life.

Question 51

What are the stages of the water cycle?

Answer 51

• energy from the Sun evaporates water from oceans, lakes, seas etc.
• the water cools as it rises, and condenses to form water vapour, which forms clouds
• as the water droplets get too large or heavy, they fall as rain, snow or hail (precipitation)
• the water is returned to the ocean through surface runoff and leaching
• some water goes straight back to the air by transpiration

Question 52

What is desalination?

Answer 52

The process of obtaining fresh water from the sea of salty water. Several methods are used to do this, such as distillation, where the water is evaporated then condensed and collected.