3.5 population size and ecosystems

Question 1

Define population

Answer 1

an interbreeding group of organisms of the same species occupying a particular habitat.

Question 2

Define birth rate

Answer 2

the reproductive capacity of a population; the number of new individuals derived from reproduction per unit time.

Question 3

Define immigration

Answer 3

The movement of individuals into a population of the same species.

Question 4

Define equilibrium species

Answer 4

Species that control their population by competition rather than by reproduction and dispersal

Question 5

Define death rate

Answer 5

the number of deaths over a given period, usually a year, divided by the number of adults in a population.

Question 6

Define carrying capacity

Answer 6

the maximum number around which a population fluctuates in a given environment

Question 7

Define environmental resistance

Answer 7

Limiting factors cause environmental resistance preventing population growth

Question 8

Define abiotic

Answer 8

a part of the environment of an organism that is non living e.g air (usually dencity independent)

Question 9

Define biotic

Answer 9

A part of the environment that is living e.g pathogens, predators. (usually density dependent )

Question 10

Define density dependent

Answer 10

their effect increases as the density of the population increases e.g depletion of food supply

Question 11

Define density independent

Answer 11

the effect of these factors does not depend on the population density. the effect is the same regardless of the size of the population

Question 12

Define intraspecific competition

Answer 12

between individuals of the same species

Question 13

Define interspecific competition

Answer 13

between individuals of different species

Question 14

Calculation of rate of growth is…

Answer 14

antilog5-antilog2 / no of days

Question 15

Describe the carbon cycle:

Answer 15

• carbon found as co2 in atmosphere and dissolved in water
• co2 from atmosphere absorbed by green plants in photosynthesis
• enters consumers when they feed on plants and each other

Question 16

How does co2 get into atmosphere?

Answer 16

• when organisms respire
• burning fossil fuels
• decomposers

Question 17

carbons recycling pathway in the sea:

Answer 17

• marine organisms use carbonates to make shells
• when they die shells fall to ground forming limestone rocks
• carbon in these rocks return to atmosphere as co2 during volcanic eruptions or weathering

Question 18

human impacts on the carbon cycle:

Answer 18

• combustion of fossil fuels
• deforestation as photosynthesis is reduced and the trees may be burned or left to decay which release co2

Question 19

rising co2 levels leads to:

Answer 19

• global warming which is an increase of average global temp believe to be a consequence of the greenhouse effect
  e.g polar ice melting and forest fires
• climate change which is a consequence of global warming. Changes in climate patterns and extreme weather conditions- drought
  people suffer from crop yield reductions and failed harvests, there is a use of drought tolerant crops

Question 20

what is carbon footprint?

Answer 20

• the equivalent amount of co2 generated by an individual, product or service in one year.
  we must reduce reuse recycle

Question 21

Human impact on nitrogen cycle:

Answer 21

-farmers use pesticides to reduce damage to crops
-use nitrogen based fertilisers such as ammonium nitrate to increase plant growth
-plough and drain soil to improve soil aeration, favours aerobic processes of N-fixation and nitrification and inhibiting dentrification which is anaerobic, allowing air to reach plant roots as nitrates taken up by active transport requiring atp.
-manure + slurry- contains nitrogen and improves soil structure

Question 22

consequence of using water- soluble nitrate fertilisers

Answer 22

• washed off into rivers increasing the ion content (eutrophication- artificial enrichment of aquatic habitats caused by run off fertilisers)
  -increase in nitrates leads to algal bloom blocking light to aquatic plants
• as plants die they form detritus which is decomposed aerobically using dissolved o2 in the water
• causing other aerobic organisms/ fish to die
• only anaerobic bacteria survive releasing ammonium into the water- toxic

Question 23

to reduce fertiliser run off:

Answer 23

• apply when plants are actively growing so it’s readily used and doesn’t build up in soil
• not apply within 10m of watercourses
• dig drainage ditches to collect any run off