Population controlling etc.

Question 1

what is the definition of species

Answer 1

a group of similar organisms that can interbreed to produce fertile offspring using homologous pairs at meiosis

Question 2

what is the definition of population

Answer 2

a group of organisms of a single species interbreeding and occupying a particular area (habitat)

Question 3

what are population numbers dependent on?

Answer 3

birth rate
death rate
immigration (moving in)
emigration (moving out)

Question 4

population will increase if…

Answer 4

birth rate + immigration is more than death rate + emigration

Question 5

what is the definition of carrying capacity

Answer 5

the maximum population size that can be maintained over a period of time in a particular habitat

Question 6

what types of infectious diseases can affect population growth

Answer 6

malaria, Aids/HIV, cholera, TB can be a factor in preventing population growth

Question 7

how do humans change the environment for their benefit

Answer 7

deforestation - clear land for farming, buildings etc. increasing CO2 which results to global warming
fertiliser and pesticide use - reduces biodiversity
burning of fossil fuels - increase pollution
sewage use - pollution e.g eutrophication
hunting and fishing - increases endangered species and lowers fish stocks
increased industrialisation - greenhouse gases = global warming

Question 8

what are organic molecules

Answer 8

molecules that contain carbon

Question 9

examples of organic molecules in plants

Answer 9

cellulose, phospholipid bilayer, DNA, RNA, glucose, sucrose

Question 10

what is a saprobiont

Answer 10

a decomposer of carbon molecules e.g. fungi/bacteria

Question 11

how do fungi breakdown trees

Answer 11

through enzymes (lignin) which causes extracellular digestion

Question 12

how do humans influence the carbon cycle?

Answer 12

respiration (take in oxygen, give out carbon dioxide)
burning fossil fuels - CO2
deforestation - CO2

Question 13

what is a carbon store

Answer 13

rocks such as chalk, marble and limestone which is the build up of planktons that can’t be broken down and respired.

Question 14

how does deforestation affect the carbon cycle

Answer 14

less photosynthesis meaning less oxygen

Question 15

what could happen to the carbon in organic molecules in plants

Answer 15

they could be ingested, digested or absorbed or the plant could die.

Question 16

what does decomposition mean

Answer 16

release nitrogen compounds/ammonia from dead bodies/faeces/urine

Question 17

what does nitrogen fixing mean

Answer 17

converting nitrogen gas into soluble nitrogen containing compounds

Question 18

what does denitrifying mean

Answer 18

convert nitrates into nitrogen gas, often found in anaerobic soils

Question 19

what does nitrifying mean

Answer 19

converting ammonium compounds into nitrites then into nitrates

Question 20

what bacterias are found in the nitrogen cycle?

Answer 20

nitrosomonas
nitrobacter
azotobacter
rhizobium

Question 21

what does nitrosomonas do?

Answer 21

converts ammonium ions to nitrites (a nitrifying bacteria)

Question 22

what does the nitrobacter do

Answer 22

converts nitrites to nitrates (a nitrifying bacteria)

Question 23

what does azotobacter do

Answer 23

a nitrogen fixing bacteria that lives free in the soil

Question 24

what does rhizobium do

Answer 24

a nitrogen fixing bacteria found in lumps on the roots of legume plants called root nodules

Question 25

what do plants need nitrogen for

Answer 25

to build amino acids (nitrogen found in amino group)

to build organic bases which make nucleotides and nucleic acids for DNA and RNA

Question 26

why cant plants take nitrogen from air

Answer 26

because they can only take in nitrogen in the form of ammonia or nitrates (NH3 or NO3) through their roots.

Question 27

what type of relationship do plants and rhizobium have and why?

Answer 27

rhizobium and plants have a symbiotic relationship where the bacteria benefits by having food and shelter and the plants benefit by gaining nitrates produced by the bacteria

Question 28

examples of leguminous plants

Answer 28

peas, beans and clovers