B7 - Ecology

Question 1

What is a habitat?

Answer 1

A place where an organism lives

Question 2

What is a population?

Answer 2

The total number of organisms of the same species living in the same geographical area.

Question 3

What is an Community?

Answer 3

A community is the population of all the DIFFERENT species that live in the same habitat.

Question 4

What does biotic mean?

Answer 4

Living organism

Question 5

What does abiotic mean?

Answer 5

non-living parts of the environment such as water or minerals in the soil.

Question 6

What is an Ecosystem?

Answer 6

• An ecosystem is the interaction of a community of living organisms with the non-living (abiotic) parts of their environment
• Ecosystems can vary greatly in size and scale. Some ecosystems are small – a single tree can be seen as an ecosystem. Some ecosystems are very large – the whole of Antarctica can be seen as one ecosystem.
• Some other examples of ecosystems include:
  
  • A garden pond
  • A woodland
  • A coral reef
  • A desert

Question 7

What does it mean if animals have to compete?

What are the two types of competition

Answer 7

• If a group of organisms all need the same resource in order to survive and reproduce (have offspring) but there is a limited amount of the resource available, they are said to compete for the resource
• Competition can be between members of the same species (intraspecific competition)
  or between members of different species (interspecific competition)

Question 8

What is an Adaptation?

Answer 8

• If an organism has characteristics that help it to survive and reproduce in its habitat, it is said to be adapted to its habitat

Question 9

How will species interact in an Ecosystem?

Answer 9

• In order to survive and reproduce (have offspring), organisms need certain resources from their surroundings (from the ecosystem they are living in)
• This means that members of a species will often interact with members of its own species or other species
• Some examples of these interactions include:
  
  • Predators (carnivores) eating prey
  • Herbivores eating plants
  • Plant species being pollinated by bees

Question 10

What do Plants compete for?

Answer 10

• Plants in a community or habitat may compete with each other for certain limited resources:

Question 11

What do Animals compete for and why?

Answer 11

• Animals in a community or habitat may compete with each other for certain limited resources:

Question 12

What is meant by Interdependece?

What is a stable community?

Answer 12

• Within a community, each species depends on other species for food, shelter, pollination, seed dispersal so If one species is removed it can affect the whole Community
• This is called interdependence
• A stable community is one where all the species and environmental factors are in balance so that population sizes remain fairly constant

Question 13

Give an example of Interdependence?

Answer 13

• For example, in the food web above, if the population of earthworms decreased:
  
  • The population of grass plants would increase as there are now fewer species feeding off them
  • The populations of frogs and mice would decrease significantly as earthworms are their only food source
  • The population of sparrows would decrease slightly as they eat earthworms but also have another food source to rely on (caterpillars)

Question 14

What are all the Abiotic factors?

Answer 14

• In Biology, ‘abiotic’ means non-living. An abiotic factor is a non-living factor
• Some abiotic factors which can affect a community are shown in the table below:
• Light Intensity
• Co2 concentration for plant
• O2 concentration for aquatic life
• Temperature
• pH and mineral concentration of soil
• Moisture levels
• Wind intensity for transpiration

Question 15

Plants of the same species were grown in tanks with different CO₂ levels. Their height was measured after 3 weeks and an average taken:

What conclusion can you draw from this graph about the effect of CO₂ concentration on plant growth rate? Explain your answer.

Answer 15

As CO₂concentration increases, average plant height also increases.

For example, at 5% CO₂, average plant height was 10cm, but at 30% CO₂, average plant height was 60cm. This shows that the higher the CO₂concentration, the greater the plant growth rate.

This is because CO₂ is used by plants for photosynthesis, which allows the plant to produce glucose for energy to grow.

Question 16

What are the Biotic factors?

Answer 16

Biotic (living) factors which can affect a community are:

• Availability of food
• New predators arriving
• New pathogens
• One species outcompeting another so the numbers are no longer sufficient to breed

Question 17

Example exam question

A study recorded the number of red and grey squirrels in a particular woodland habitat for 20 years. Grey squirrels were introduced to the habitat in year 6 of the study.

What conclusion can you draw from this graph about the effect of introducing grey squirrels to a habitat that is occupied by red squirrels? Explain why this might have occurred.

Answer 17

As the number of grey squirrels increases, the number of red squirrels decreases.

This might have occurred because the two squirrel species are competing for one or more of the same resources.

Grey squirrels are better adapted to use these resources and have outcompeted the red squirrels until eventually there are too few red squirrels left to breed successfully and there are none left in the habitat.

TEST

Question 18

What are Producers?

Answer 18

Photosynthetic organisms are the producers of biomass for life on Earth

• They produce their own food using energy from the Sun
• A producer has the following characteristics:
• • They are at the start of every food chain
    
    • They can photosynthesise
    • They make glucose by photosynthesis & They use this glucose to produce other biological molecules, which then make up the producer’s biomass
    • In extreme environments (such as underwater volcanic vents) the producers are not photoautotrophs but chemoautotrophs who produce organic molecules without using energy from the Sun)

Question 19

What are the Features of food chain?

What does a food chain show?

Answer 19

• A simple way to show the feeding interactions between the organisms in a community is with a food chain

1. ​Producer: food chains always begin with a producer
2. Primary consumer: producers are eaten by primary consumers (herbivores/omnivores)
3. Secondary consumer: primary consumers are eaten by secondary consumers (carnivores/omnivores)
4. Tertiary consumer: secondary consumers are eaten by tertiary consumers (carnivores/omnivores)

• A food chain shows the transfer of energy from one organism to the next
• The source of all energy in a food chain is light energy from the Sun
• The arrows in a food chain show the transfer of energy from one level of the food chain to the next

Question 20

What is the producer?
What is the Primary Consumer?
What is the secondary consumer?

Answer 20

Question 21

How do scientists investigate Ecosystems?

Answer 21

• Ecology is the branch of biology that studies the distribution and abundance of species, the interactions between species, and the interactions between species and their abiotic environment
• Ecologists are biologists that study these interactions by investigating ecosystems
• You need to know how ecologists determine the distribution and abundance of species in an ecosystem using quadrats and transects
• You need to understand how they use quadrats and transects in order to do this

Question 22

What are Quadrats used for?

Answer 22

Quadrats

• Quadrats are square frames made of wood or wire & They can be a variety of sizes eg. 0.25m² or 1m²
• They are placed on the ground and the organisms within them are recorded
• They can be used to measure the abundance of plants or slow-moving animals

Quadrats can be used to measure abundance by recording:

• The number of an individual species: the total number of individuals of a single species (eg. buttercups) is recorded
• Species richness: the total number of different species (but not the number of individuals of each species) is recorded
• Percentage cover: the approximate percentage of the quadrat area in which an individual species is found is recorded (this method is used when it is difficult to count individuals of the plant species being recorded eg. grass or moss

Question 23

What are Transects used for?

Answer 23

• A transect is used to measure how the abundance of a species changes as you move along a changing habitat
  
  • A line called a transect is set up through the changing habitat you want to investigate with a tape measure
  • A quadrat is placed at regular intervals along the transect (eg. every 5 metres)
  • At each interval, the quadrat can be used to record the number of an individual species, species richness or percentage cover
• Transects are useful for investigating how the abundance of a species is affected by an abiotic factor (e.g. light intensity, moisture levels, soil depth, altitude etc)

Question 24

Answer 24

For Median Put them in order and if there are two middle values add them together and divide by two

Question 25

Answer 25

Question 26

What is the general trend in Predator-prey cycles?

Answer 26

1. The number of predators increases as there is more prey available
2. The number of prey then decreases as there are now more predators
3. The number of predators decreases as there is now less prey available
4. The number of prey increases as there are now fewer predators
5. The cycle now repeats

This is only true in a stable community. If something changed e.g. a drought or a new predator joins the game then the cycle would change

Question 27

How is carbon Recycled in the enviroment?

Answer 27

• Elements such as carbon are not endless resources
• There is a finite amount of each element on the planet
• Elements need to be recycled in order to allow new organisms to be made and grow

The main processes of the carbon cycle

• Carbon is taken out of the atmosphere in the form of carbon dioxide by plants and algae during photosynthesis.
  (the carbon is used to make glucose, which can be turned into carbohydrates, fats and proteins – biomass – within plants and algae)
• This carbon is passed on to animals (and microorganisms) when they feed on plants and algae
• It is returned to the atmosphere in the form of carbon dioxide, during respiration by PLANTS, animals and microorganisms (that release CO₂ during decomposition)
• Then when these organisms die their waste and dead remains are decomposed aerobically by decomposers which means CO2 is returned to the atmosphere.
• If animals and plants die in conditions where decomposing microorganisms are not present, the carbon in their bodies can be converted, over millions of years and significant pressure, into fossil fuels
• When wood or fossil fuels are burned (a process is known as combustion), the carbon within them combines with oxygen and carbon dioxide is released into the atmosphere

Question 28

What are the main parts of the carbon cycle that involves organisms?

Answer 28

The main parts of the carbon cycle involving living organisms are:

• Carbon is taken out of the atmosphere by producers via photosynthesis
• It is passed on to animals and decomposers by feeding
• It is returned to the atmosphere by respiration; in plants, in animals and in decomposing microorganisms

Don’t forget – photosynthetic organisms like plants respire too, returning carbon dioxide to the atmsphere! In addition, carbon dioxide isturned to the by combustion of wood and fossil fuels.You should be able to identify what each arrow represents in any diagram of the carbon cycle.

Question 29

How is water recycled?

Answer 29

• The water cycle provides fresh water for plants and animals on land before draining into the seas
• Water enters the atmosphere as water vapour in one of two processes
  
  • Energy from the Sun heats the Earth’s surface and water evaporates from oceans, rivers and lakes
  • Transpiration from plants releases water vapour into the air
• The warmer air of the lower atmosphere rises, taking the water vapour with it
  
  • The moist air cools down as it rises
  • Water vapour condenses back into liquid water, forming clouds
• Water returns to Earth in the form of precipitation
  
  • As the water droplets in the cloud get bigger and heavier, they begin to fall as rain, snow and sleet
  • This is called precipitation

Question 30

What are the main processes of the water cycle?

Answer 30

• Evaporation & Transpiration
• Condensation
• Precipitation

Question 31

What role do micro-organisms play in recycling?

What are examples of decomposers

Answer 31

• They return carbon to the atmosphere as carbon dioxide and mineral ions to the soil
  
  • When living organisms produce waste products or organisms die, the waste products and dead organisms are digested by microorganisms known as decomposers
  • Bacteria and fungi are the main groups of decomposers
• *​**
• Decomposition is the process by which waste products or dead organisms are broken down and the materials they contain (such as carbon and mineral ions such as iron, magnesium and nitrates) are returned to the environment
• When decomposing microorganisms respire, carbon is returned to the atmosphere in the form of carbon dioxide

Question 32

What Factors effect the rate of Decay?

Answer 32

Temperature - Higher temperatrues mean enzymes involved in decomposition work faster but if it is too high the enzymes will denature. Too low and they will work slowly.

Water - Decomposers require water to survive. Many decomposers also function by secreting enzymes onto decaying biological matter and absorbing the products of chemical digestion - without water this cannot occur.

• *Availability of Oxygen** - Oxygen is needed by many decomposers respiration - without oxygen, they cannot survive.
• *For these decomposers, the rate of decay decreases as oxygen availability decreases.** Some do it anaerobically.

Question 33

Answer 33

Question 34

Why is recycling water and carbon important?

Answer 34

The carbon cycle returns carbon from organisms to the atmosphere as carbon dioxide to be used by plants in photosynthesis.

The water cycle provides fresh water for plants and animals on land before draining into the seas. Water is continuously evaporated and precipitated.

Question 35

How is Decomposition used in Compost?

Answer 35

Compost

• Gardeners and farmers try to provide optimum conditions (warmth, moisture and an oxygen supply) for rapid decay of waste biological material (eg. waste plant matter)
• The compost produced is used as a natural fertiliser for growing garden plants or crops
• Once the compost is spread onto the soil, it is broken down further by decomposing microorganisms (bacteria and fungi) and detritivores (eg. earthworms and woodlice)
• This ensures the recycling of minerals (such as magnesium and nitrates) that can then be absorbed by plants to be used for growth
• (magnesium is used to make chlorophyll, nitrates to make amino acids)

Question 36

How is decomposition used in biogas?

Answer 36

• Some decomposing microorganisms can break down biological material without oxygen
• This is called anaerobic decay
• Anaerobic decay produces methane gas (as well as carbon dioxide) – together these products are given the term ‘biogas’
• The methane produced can be burned as a fuel:

methane + oxygen → carbon dioxide + water

• Biogas generators are large containers in which animal or plant waste is allowed to decay anaerobically

Question 37

What are some changing environmental factors that affect the distribution of organisms?

Answer 37

• A change in distribution means a change in where an organism lives
• Some changing environmental factors that can affect the distribution of organisms include:
  
  • Temperature
  • Availability of water
  • Composition of atmospheric gases
• These changes may be seasonal, geographic or caused by human interaction

Question 38

How does Temperature affect the distribution of species?

How can temperature change?

Answer 38

• Organisms have adaptations that enable them to survive within a certain temperature range
• As climate change occurs and average temperatures rise, the distribution of species is changing
• Eg. the distribution of some plant, bird and insect species in Europe is spreading northwards into areas they were not previously able to inhabit, as these areas now have higher average temperatures as a result of global warming

Question 39

How does The availability of water affect the distribution of species?

How can Availability of water change?

Answer 39

• All organisms require water to survive, either directly **or indirectly (water may
• provide a habitat for species and is
• essential for the growth of plants that support whole food chains and food webs)**
• Eg. every year in Africa, wildebeest migrate first northwards and then southwards again, following the rainfall as this provides them with fresh grazing and water

Question 40

How does composition of atmospheric gases affect the distribution of species?

How can the composition of gases change?

Answer 40

• There are many ways in which the distribution of organisms can be affected by atmospheric gases:
  
  • Oxygen is required for aerobic respiration in plants and animals
  • Some aquatic animals (such as fish) can only survive in water with high oxygen concentrations
    
    • As pollution increases in freshwater systems, growth of anaerobic microorganisms is encouraged which can lead to a drop in oxygen when they die as a result of decomposition, fish cannot survive in these conditions
  • Carbon dioxide is required for photosynthesis in plants
  • Some species are very sensitive to air pollution
    
    • Eg. some species of lichen are not able to grow where sulphur dioxide is present (produced during certain industrial processes due to the combustion of fossil fuels)

Question 41

What is Biodiversity?

Why is a high biodiversity good?

Answer 41

• Biodiversity is the variety of all the different species of organisms on earth, or within an ecosystem. A great biodiversity ensures the stability of ecosystems by reducing the dependence of one species on another for food, shelter and the maintenance of the physical environment. The future of the human species on Earth relies on us maintaining a good level of biodiversity. Many human activities are reducing biodiversity and only recently have measures been taken to try to stop this reduction.
• For example, for the food web below:
  • If the mouse population was suddenly wiped out, the fox and the hawk populations might decrease but would not be wiped out too, as mice are not their only food source
  • This example ecosystem has sufficient biodiversity to support the fox and hawk populations
  • The fox population can still depend on the rabbit and frog populations for food
  • The hawk population can still depend on the frog and sparrow populations for food

Question 42

Why is human population increasing and what does this mean for the amount of waste produced?

Answer 42

• Human population growth globally has been increasing exponentially for the last 150 years

There are many reasons for this exponential growth, including:

• Improved technology leading to an abundance of food = rapid increase in birth rate
• Improved medicine, hygiene and health care = decrease in death rate
• Rapid growth in the human population and an increase in the standard of living mean our negative effect on the environment is also increasing
• As increasingly more resources are used to sustain the growing human population, more waste is produced and more pollution is created
• Unless waste and chemical materials are properly handled, pollution will continue to be created

Question 43

What are sources of water pollution and its effects?

Answer 43

Pollution can occur:

Pollution kills plants and animals which can reduce biodiversity

• Toxic Chemicals
• Water Pollution
• Fertilisers

Question 44

What are sources of land pollution and their effects?

Answer 44

Landfills
Chemicals such as pesticides and herbicides

Question 45

What are sources of air Pollution and their effects?

Answer 45

Question 46

How is land use decreasing biodiversity?

Answer 46

• The increasing human population of the planet means an increasing amount of land is required for activities such as building, quarrying, farming and dumping waste & This is causing the destruction of many habitats, such as rainforests and woodlands
• This reduces the biodiversity of these areas and interrupts food chains and webs, meaning that more species may die because their prey is gone

Question 47

What are Peat bogs?
Why are they being destroyed and what are the consequences of this?

Answer 47

• Bogs are areas of land that are waterlogged and acidic – b do not decay fully when they die due to a lack of oxygen
• The partly decomposed plant matter accumulates over very long periods of time and forms peat
• The carbon that would have been released into the atmosphere as carbon dioxide (if the plants had been able to fully decompose) is instead stored in the peat
• Peat bogs are also important habitats for many species (eg. migrating birds)

Why they are being destroyed

• Peat bogs are drained so that the area can be used for farming
• Peat can be dried and used as a fuel
• Peat can be used to produce compost for gardens or farms to increase food production

Negative impavts

• Carbon dioxide is released into the atmosphere when peat is burned as a fuel – this contributes to global warming
• Similarly to fossil fuels, peat bogs take so long to form that peat is effectively a non-renewable energy source
• The available peat bog habitat area for many species of animals, plants and microorganism is decreasing, reducing biodiversity
• Peat bogs are being destroyed faster than they can form – they are being used unsustainably

Question 48

What are greenhouse gases and how do human activities lead to increased amounts of carbon dioxide and methane?

Answer 48

• A greenhouse gas is a gas that absorbs infrared radiation from the Sun so it remains trapped in the Earth’s atmosphere
• This is important to ensure Earth is warm enough for life, however if levels of these gases in the atmosphere increase it leads to an increase in the greenhouse effect which causes the Earth’s average temperature to rise
• There are many greenhouse gases, the most important are:
  
  • Water vapour
  • Carbon dioxide
  • Methane
  • Nitrous oxides
  • CFCs
• Human activities have led to increasing levels of carbon dioxide and methane in the atmosphere:
  
  • Carbon dioxide is produced during the combustion of fossil fuel
  • Methane is produced by cattle as they digest grass and released by rice paddy fields

Question 49

What is the greenhouse effect?

Answer 49

• The Sun emits rays that enter the Earth’s atmosphere
• The heat bounces back from the Earth’s surface
• Some heat is reflected back out into space
• Some heat is absorbed by greenhouse gases and is trapped within the Earth’s atmosphere – this is normal
• However, as the levels of greenhouse gases in the atmosphere rise due to human activities the Earth’s average temperature rises beyond normal (an enhanced greenhouse effect), causing global warming

Question 50

What are the consequences of Global Warming and what evidence is there for this?

Answer 50

The consequences of global warming

• The consequences of global warming due to an enhanced greenhouse effect include:
  
  • Ocean temperatures increasing, causing melting of polar ice caps / rising sea levels / flooding / coral bleaching
  • Increasing temperatures causing extreme weather like super storms, flooding, droughts
  • Changes in or loss of habitats due to these extreme weather events
  • Decreases in biodiversity as food chains are disrupted and extinction rates increase
  • Increases in migration of species to new places, including increased spread of pests and disease

The evidence for global warming

• There is scientific consensus (almost all scientists agree) that global warming is happening and that human activities are largely responsible for the most recent warming
• This scientific consensus is based on systematic reviews of thousands of scientific research papers that have been ‘peer reviewed’ by other scientists (the method used by scientists to check each other’s work in order to ensure that research findings are valid)
• Although they can make good predictions, it is difficult for scientists to say for certain what the consequences of global warming will be

Question 51

What energy transfers take place between Trophic levels?

Answer 51

• This chemical energy is then transferred to primary consumers as they consume (eat) producers
• The chemical energy is then transferred from one consumer to the next as they eat one another
• Apex predators are at the very top of the food chain – they are carnivores with no predators. The chemical energy stored within apex predators can be passed on to decomposers when apex predators die and are decomposed

Question 52

How do decomposers decompose?

Answer 52

• The two main groups of decomposers are bacteria and fungi
• Decomposers carry out a very important function in ecosystems – they break down dead plant and animal material
• They do this by:
  
  • Secreting digestive enzymes onto the surface of the dead organism
  • These enzymes break down the dead matter into small soluble food molecules
  • These molecules are then absorbed by the decomposers
• This process of decomposition also helps to release organic nutrients back into the environment (eg. the soil) which are essential for the growth of plants (producers)

Question 53

What is Biomass?

Answer 53

• Biomass is the mass of living tissues (or recently dead tissues that have not yet been decomposed) that a plant or animal is made up of
  
  • For example, the wood of a recently fallen tree is still biomass, even though the organism is no longer alive
• It is the ‘dry mass’ of the organism (how much mass the plant or animal would have without including all the water that is in the organism)
• There is always less and less biomass as you move up through the trophic levels in a food chain or food web
• For example, for the simple food chain below, if we added up the total biomass of all the grass in this particular ecosystem, it would be greater than the total biomass of all the grasshoppers, which would in turn be greater than the total biomass of all the frogs

Question 54

How is Biomass transferred?

Answer 54

• Energy flows from the Sun to the first trophic level (producers) in the form of light
• Producers convert light energy into chemical energy
  
  • This occurs during photosynthesis, which makes glucose
• Producers use this glucose (during respiration) to produce their own biomass
  
  • Biomass is a store of chemical energy
• When primary consumers consume producers, they break down the biomass of the producer (digestion) and use the chemical energy to increase or sustain their own biomass
• When secondary consumers consume (eat) primary consumers, they break down the biomass of the primary consumer (digestion) and use the chemical energy to increase or sustain their own biomass, and so on
• In this way, as chemical energy is transferred from one trophic level to the next, biomass is also transferred

Question 55

How is Biomass lost?

Answer 55

• Not all biomass is transferred to the next level
• Approximately, only 10% of the biomass of each trophic level is passed on to the next
• This is why food chains are rarely made up of more than six trophic levels – the total amount of biomass available eventually becomes too small to support another trophic level
• *Losses of biomass** are due to:
  
  • Organisms rarely eat every part of the organism they are consuming – some of the biological material of plants and animals may be inedible (eg. many predators do not consume the bones of their prey)
  • Not all the ingested material is digested and absorbed, some is egested as faeces
  • Some absorbed material is lost as waste:
    
    • Carbon dioxide and water are waste products of respiration (when glucose is used by an organism to provide energy for moving and keeping warm, rather than to produce more biomass)
    • Water and urea are the waste products in urine

Question 56

Answer 56

Question 57

What is Food security and what are biological factors that affect food production?

Answer 57

• Food security is having enough food to feed a population. Food security gives an indication of how much food is available
• Sustainable methods of farming and producing food are needed in order to overcome food shortages and help populations whose food security is under threat
• Sustainable food production involves making enough food but ensuring this is done without using resources (such as water and soils) faster than these resources can be renewed and used again

DEPPCC

Question 58

How can the efficiency of farming techniques improved?

Answer 58

• The efficiency of food production can be improved by restricting energy transfer from food animals to the environment. This can be done by:
  
  • limiting their movement – livestock are kept in small pens or cages so that they use less energy moving around
  • controlling the temperature of their surroundings – livestock are kept at their optimum temperature so that they use less energy regulating their body temperatures themselves
• If livestock don’t have to carry out these processes(respiration), there is more energy available for growth
• In addition, some animals are fed high protein foods to increase growth

Question 59

What are some advantages and disadvantages of modern farming techniques?

Answer 59

• Some people have ethical objections to some modern intensive farming methods
• Keeping livestock in very confined spaces (factory farming) is controversial because disease can spread easily and many people think it is unethical to make animals live in unnatural and uncomfortable conditions

Question 60

Factors which affect food security

Answer 60

• the increasing birth rate has threatened food security in some countries
• changing diets in developed countries means scarce food resources are transported around the world
• new pests and pathogens that affect farming
• • environmental changes that affect food production, such as widespread famine occurring in some countries if rains fail
• • the cost of agricultural inputs
• • conflicts that have arisen in some parts of the world which affect the availability of water or food.