organisms and their environments

Question 1

the flow of energy:

Answer 1

• Starts with the sun
• Green plants and algae convert light energy from the sun into chemical energy in the form of carbohydrates
• Plants use the food made by photosynthesis to grow parts such as leafs, stems, fruits etc.
• These parts are then eaten by animals - the chemical energy of the plant is then transferred to the animal’s body
• If this animal is then eaten by a second animal, the chemical energy of the first animal is transferred to the body of the second animal

Question 2

food chain

Answer 2

shows the direction of energy from one organism to the next

Question 3

food web

Answer 3

network of interconnected food chains

Question 4

pyramid of energy

Answer 4

shows the amount of energy available in the form of biomass at each trophic level

Question 5

how is energy lost (herbivores)?

Answer 5

• Herbivores:
  - not all of the plant is eaten, for examplethe roots may not be eaten by the herbivore
  - energy is used to build inedible tissues such as wood (cellulose) or roots
  - energy is lost as heat during respiration (this occurs in all living organisms, including decomposers)

Question 6

how is energy lost (carnivores)?

Answer 6

• Carnivores:
  - energy is lost as heat
  - energy is lost as excretory products (for example, urea)
  - energy is used to build up inedible parts such as bones

Question 7

What are the 4 main reservoirs that carbon is stored in/cycles between?

Answer 7

• The atmosphere
• The ocean
• Land biomass
• Fossil fuels

Question 8

how is carbon dioxide returned to the air?

Answer 8

• respiration
• combustion

Question 9

how is carbon dioxide removed from the air?

Answer 9

• Through photosynthesis by converting carbon dioxide into carbohydrates

Question 10

nitrogen fixation

Answer 10

nitrogen gas to ammonium ions

Question 11

what are the two main ways in which nitrogen fixation happens

Answer 11

lightning
bacteria

Question 12

what do nitrogen fixing bacteria do?

Answer 12

they convert nitrogen gas in the air between soil particles to form ammonia which dissolves to ammonium ions

Question 13

denitrification

Answer 13

nitrate ions to nitrogen gas

Question 14

nitrification

Answer 14

ammonium ions to nitrate ions

Question 15

how do plants absorb nitrate ions?

Answer 15

• Through root hair cells
• Through active transport

Question 16

deamination

Answer 16

the removal of the nitrogen-containing part of amino acids to form urea. Which is then secreted in the form of urine

Question 17

decomposition

Answer 17

proteins to ammonium ions

Question 18

population

Answer 18

group of organisms of one species, living in the same area at the same time

Question 19

community

Answer 19

all the populations of different species in an ecosystem

Question 20

ecosystem

Answer 20

unit containing the community of organisms and their environment, interacting together

Question 21

Factors affecting the number of individuals within a population:

Answer 21

• food supply
• predation
• disease
• competition

Question 22

Factors affecting how the size of a population changes over time:

Answer 22

1. Number of births: this increases the population size because offspring are added.
2. Immigration: this increases the size of the population because individuals come into the area from somewhere else.
3. Number of deaths: this decreases the population size because some individuals are eaten, or die of old age or illness.
4. Emigration: this decreases the size of the population because individuals leave the area to go somewhere else

Question 23

carrying capacity

Answer 23

maximum number of organisms that an ecosystem can support