ECOSYSTEMS

Question 1

Habitat

Answer 1

Place where organisms live

Question 2

Population

Answer 2

All organisms of one species in a habitat

Question 3

Producer

Answer 3

An organism that produces organic molecules using sunlight energy

Question 4

Consumer

Answer 4

An organism that eats other organisms

Question 5

Decomposer

Answer 5

An organism that breaks down dead or undigested organic material

Question 6

Trophic level

Answer 6

Stage in food chain occupied by a particular group of organisms

Question 7

Ecosystems

Answer 7

All the organisms living in a certain area and all the non-living conditions found there

Question 8

Factors involved in an ecosystem

Answer 8

Biotic factors- living feature of an ecosystem

Abiotic factors- non living features of an ecosystem (temp, rainfall, shape of land and soil nutrient availability)

Question 9

Biomass transfer

Answer 9

Main route of energy entrance is by photosynthesis, they store energy as biomass
Transferred when organisms eat eachother
Energy locked up in things that can’t be eaten eat recycled back into the ecosystem by decomposers

Question 10

Food chains

Answer 10

Simple lines of energy transfer

Question 11

Food web

Answer 11

Lots of food chains in an ecosystem and how they overlap

Question 12

How is some energy lost

Answer 12

Light reflected from sunlight when it’s the wrong wavelength
Some parts of organism aren’t eaten
Some indigestible parts are passed through as faeces
Respiration and movement
Some stored as biomass

Question 13

Net productivity

Answer 13

Amount of energy that’s available to the next trophic level

Gross productivity - respiratory loss

Question 14

Human activities increasing energy transfer

Answer 14

Herbicides kill weeds which are competing with agricultural crops for energy
Fungicides kill fungal infections which damage agricultural crops
Insecticides kill insects that eat and damage crops
Natural predators eat pest species
Fertilisers are chemicals providing crops with minerals for growth
Rearing livestock intensively involves controlling the conditions they live in so more energy is used for growth and less for other activities (animals kept in warm places where movement is restricted and fed food higher in energy)

Question 15

The carbon cycle

Answer 15

Carbon from air and water is absorbed by plants when they carry out photosynthesis- it becomes carbon compounds in plant tissues
Carbon passed on to primary consumers when they eat the plants
All living organisms die and the carbon compounds in the dead organisms are digested by microorganisms called decomposers
Carbon returned to the air by respiration
Organic matter can turn into fossil fuels over millions of years, the carbon in these fossil fuels are released when they’re burnt- combustion
Limestone and chalk composed of calcium carbonate
Carbon drawn down deep into earth crust by the movement of tectonic plates where they undergo chemical changes and release carbon dioxide which is returned by volcanoes
Rocks become weathered and combine with carbon containing compounds
Carbon dissolved into the sea and deep into the ocean by currents

Question 16

The 4 steps of the nitrogen cycle

Answer 16

Nitrogen fixation
Anmonification
Nitrification
Denitrification

Question 17

Nitrogen fixation

Answer 17

Nitrogen gas is released into the atmosphere and turned into ammonia by bacteria such as Rhizobium and Aztobacter
Ammonia then used by plants
Rhizobium are found inside root nodules in leguminous plants and form a mutualistic relationship with the plants providing them with nitrogen compounds and the plant provides them with carbohydrates
Aztobacter- found living in the soil and do not form mutualistic relationships with plants

Question 18

Ammonification

Answer 18

Nitrogen compounds from dead organisms and animal waste are turned into ammonia by decomposers which goes on to form ammonium ions

Question 19

Nitrification

Answer 19

Ammonium ions in the soil are changed into nitrogen compounds that can be used by plants
Nitrifying bacteria called Nitrosomonas change ammonium ions into nitrites
Other nitrifying bacteria called Nitrobacter change nitrites into nitrates

Question 20

Denitrification

Answer 20

Nitrates in the soil are converted into nitrogen gas by denitrifying bacteria
They use nitrates in the soil to carry out respiration and produce nitrogen gas
Happens under anaerobic conditions

Question 21

Succession

Answer 21

Process by which an ecosystem changes overtime

The biotic conditions change as the abiotic conditions change

Question 22

Primary succession

Answer 22

Happens on land that has been newly formed or exposed, there is no soil or organic material to begin with
Species colonise a new land surface
Spores and seeds are blown in by the wind and plants begin to grow
The first species to colonise are called pioneer species
Abiotic conditions are hostile, only pioneer plants grown because they are specialised to cope and grow in harsh conditions (e.g marram grass)
Pioneer species change the abiotic conditions (when they die microorganisms decompose the dead organic material forming soil)
The conditions become less hostile so new organisms can grow
These new organisms die and decompose which adds more organic material making the soil deeper and richer in minerals
Larger plants like shrubs can start to grow which retains more water
As more plants move in, more habitats are made

Question 23

Secondary succession

Answer 23

Happens at the same time but because there is already a soil layer, succession starts at a later stage
Pioneer species larger than in primary succession

Question 24

Example of primary succession

Answer 24

Lichens grow on and break down rocks releasing minerals
Lichens die and are decomposed helping to form a thin soil, this thickens as more organic material is formed which means species like mosses can grow
Larger plants (flowering plants and grasses) that need more water move in as the soil deepens 
Shrubs, ferns and small trees begin to grow and outcompete the grasses and smaller plants to become the dominant species, diversity increases
Soil is deep and rich enough in nutrients to support large trees, these become dominant species and the climax community is formed

Question 25

Climax community

Answer 25

Ecosystem is supporting the most complex community of plants and animals it can, it’s won’t change much more and is at a steady state

Question 26

Climax community in temperate climates

Answer 26

Contains large trees because they can grow in the conditions when soil has developed

Question 27

Climax community in polar climate

Answer 27

Large trees will not be able to grow so the climax contains only herbs or shrubs

Question 28

Plagioclimax

Deflected climax

Answer 28

When the succession is stopped artificially such as by humans activities
When succession is prevented by human activity but the plagioclimax that develops is different to any of the natural stages of an ecosystem

Question 29

Investigating populations

Answer 29

Abundance- number of individuals of one species in a particular area
Distribution- where a particular species is in the area you are investigating