19 Organisms and their environment

Question 1

secondary consumers

Answer 1

carnivores that eat the herbivores

Question 2

tertiary consumers

Answer 2

aka top carnivores, carnivores that eat other carnivores

Question 3

sunlight

Answer 3

the main source of energy for biological systems

Question 4

food chain

Answer 4

shows the transfer of energy from one organism to another

Question 5

food webs

Answer 5

show interconnecting food chains

Question 6

producers

Answer 6

plants that make their own organic nutrients from simple raw materials (eg carbon dioxide & water) and provide energy in the form of carbon compounds (proteins, carbohydrates & fats) for consumers and decomposers

Question 7

consumers

Answer 7

obtain their energy by eating other organisms, either plants of animals or both

Question 8

decomposers

Answer 8

fungi and bacteria that gain their energy from waste organic material

Question 9

trophic level

Answer 9

position of organisms in a food chain or food web

Question 10

primary consumers

Answer 10

herbivores that eat the producers

Question 11

pyramids of numbers

Answer 11

show how many individuals there are at each trophic level but give no indication of their size

Question 12

pyramids of biomass

Answer 12

indicate the mass of living material at each trophic level, but give no indication of the rate of growth

Question 13

energy losses

Answer 13

occur between trophic levels as a result of respiration, and in waste materials produced

Question 14

carbon cycle

Answer 14

photosynthesis, respiration, feeding, decomposition, fossilisation, combustion

Question 15

water cycle

Answer 15

evaporation, condensation, precipitation (and transpiration)

Question 16

carbon recycling

Answer 16

decomposers like bacteria & fungi are important in the recycling of nutrients

Question 17

nitrogen

Answer 17

available in the atmosphere as a gas, but not available to most organisms as it is not reactive

Question 18

nitrogen-fixing bacteria

Answer 18

live inside root nodules of legumes & convert nitrogen to ammonia

Question 19

ammonia

Answer 19

result of bacteria decomposing protein and urea.
Nitrifying bacteria convert it to nitrate ions

Question 20

Denitrifying bacteria

Answer 20

convert nitrate ions to nitrogen gas

Question 21

nitrate ions

Answer 21

absorbed by plants and converted to amino acids which they use to make proteins

Question 22

population

Answer 22

a group of individuals of the same species living in the same habitat at the same time

Question 23

population growth rate

Answer 23

affected by food supply, predation & disease

Question 24

sigmoid population growth curve

Answer 24

curve on a graph showing four main phases in the growth of a population of bacteria

Question 25

lag phase

Answer 25

first phase in the growth of a population when doubling of the numbers has little effect as the numbers are so small

Question 26

exponential (log) phase

Answer 26

second phase in the growth of a population, when the population is increasing rapidly by doubling, with no limiting factors (eg food/ water)

Question 27

stationary phase

Answer 27

third phase in the growth of a population, when cells are dying at the same rate as they are being produced

Question 28

death phase

Answer 28

fourth and final phase in the growth of a population, when more cells are dying than are being produced, because of oxygen shortage, lack of food or build-up of toxic waste products

Question 29

human population growth

Answer 29

has increased exponentially over the past 300 years due to improved agriculture, nutrition, public health & medical care

Question 30

deamination

Answer 30

Conversion of amino acids into urea.

Question 31

respiration

Answer 31

A metabolic reaction which breaks down nutrients (glucose) and releases energy

Question 32

Photosynthesis

Answer 32

Conversion of light energy from the sun into chemical energy. Formation of glucose and oxygen from carbon dioxide and water.

Question 33

nitrifying bacteria

Answer 33

Bacteria that change dissolved ammonia into nitrite compounds or nitrites into nitrate compounds.

Question 34

Denitrification

Answer 34

The process that converts nitrates from the soil into nitrogen gas.

Question 35

Nitrification

Answer 35

Ammonium ions in the soil are converted to nitrate ions in two stages: ammonium ions NH 4 + → nitrite ions NO 2 – → nitrate ions NO 3 –

Question 36

Nitrogen fixation

Answer 36

nitrogen gas to ammonium ions, by lightning and bacteria

Question 37

Decomposition

Answer 37

proteins to ammonium ions

Question 38

Absorption of nitrate ions

Answer 38

done by plants Through the root hair cells, against a concentration gradient using active transport across a cell membrane with carrier proteins using energy (from ribosomes)

Question 39

The steps of the nitrogen cycle

Answer 39

Nitrogen fixation, nitrogen assimilation, ammonification, nitrification, and denitrification.

Question 40

Why is a pyramid of numbers large at the bottom but small at the top?

Answer 40

Energy is lost between the levels There is not enough food to sustain more life Not all organisms are on just a singular trophic level