19. Organisms And Their Environment

Question 1

what is the main source of energy in biological systems

Answer 1

the sun

Question 2

describe the flow of energy in biological systems

Answer 2

• light energy from the sun is trapped by photosynthetic organisms
• energy is stored as chemical energy in organisms
• energy is eventually lost to the environment

Question 3

what is a food chain

Answer 3

a way of showing the flow of energy between organisms starting with a producer

Question 4

how is energy transferred between organisms in a food chain

Answer 4

by ingestion

Question 5

what is a trophic level

Answer 5

the position that an organism holds in a food chain, food web, pyramid of numbers or pyramid of biomass

Question 6

why are biomass transfers not 100% efficient

Answer 6

egestion
excretion
respiration
the production of inedible bones and shells

Question 7

why do food chains usually have fewer than 5 trophic levels

Answer 7

biomass transfers are not 100% efficient and so there is often not enough energy to support 5 trophic levels

Question 8

why is it most efficient to supply plants as food for humans

Answer 8

using the plants as food for livestock wastes energy as the biomass transfers are not 100% efficient

eating plant transfers can maximize the amount of energy gained as there is only on transfer

Question 9

what is a food web

Answer 9

multiple interconnected food chains

Question 10

what is a producer

Answer 10

an organism that makes its own food

Question 11

what is a consumer

Answer 11

an organism that gets its energy by eating other organisms

Question 12

what is a primary consumer

Answer 12

an organism that feeds on producers

Question 13

what is a secondary consumer

Answer 13

an organism that feeds on primary consumers

Question 14

what is a tertiary consumer

Answer 14

an organism that feeds on secondary consumers

Question 15

what are herbivores

Answer 15

herbivores are animals that only eat plants

Question 16

what are carnivores

Answer 16

organisms that mainly eat animals

Question 17

what are decomposers

Answer 17

organisms that break down dead matter

Question 18

explain the impact humans have on food chains and webs by over harvesting certain species

Answer 18

many organisms rely on other organisms for food, over harvesting can reduce the amount of food available for other animals

Question 19

explain the impact humans have on food chains and webs by introducing other species into a habitat

Answer 19

introducing new organisms increases competition and can interfere with the food chain, causing organisms who cannot compete to die

Question 20

what is a pyramid of numbers

Answer 20

a pyramid of numbers shows the number of organisms at each trophic level

Question 21

what is a biomass pyramid

Answer 21

a pyramid that shows the total dry mass of organisms at each trophic level

Question 22

why is a pyramid of biomass a better way of representing a food chain than a pyramid of numbers

Answer 22

pyramids of biomass take into account the size of the organisms and are less easily misinterpreted

Question 23

describe the carbon cycle

Answer 23

• plants fix carbon dioxide into organic molecules during photosynthesis
• the organic carbon containing molecules are passed onto organisms that eat the plants
• carbon dioxide is released back into the atmosphere by respiration from animals and plants
• burning fossil fuels also releases carbon dioxide into the atmosphere

Question 24

state the effect of burning fossil fuels on carbon dioxide concentration in the environment

Answer 24

burning fossil fuels releases more carbon dioxide into the atmosphere increasing the concentration of CO2

Question 25

state the effect f deforestation on carbon dioxide concentration in the environemnet

Answer 25

- trees take in carbon dioxide during photosynthesis - cutting down trees prevents this and so the atmospheric carbon dioxide concentration does not decrease

Question 26

describe the water cycle

Answer 26

- water from lakes and oceans evaporate - the evaporated water condense into clouds and returns to each as percipitation - the water from precipitation is useful for life on land - the water then returns to rivers and oceans through surface runoff

Question 27

why is the water cycle imporatnt

Answer 27

living organisms require water the water cycle provides organisms on land with a continuous supply of water

Question 28

describe how nitrogen is cycled through an ecosystem

Answer 28

- nitrogen is fixed by lightning and bacteria - decomposers break dead matter down into ammonium ions - nitrifying bacteria convert ammonia into nitrates and nitrites - denitrifying bacteria release nitrogen back to the atmosphere

Question 29

what is deaminiation

Answer 29

the removal of the amine group in an amino acid

Question 30

state 4 roles of bacteria in the nitrogen cycle

Answer 30

decomposition nitrification denitrification nitrogen fixation

Question 31

define population

Answer 31

a species that occupy the same habitat at the same time

Question 32

define community

Answer 32

all the different populations in an ecosystem

Question 33

define ecosystem

Answer 33

both the community and their physical environment

Question 34

state 3 factors that affect population growth rates

Answer 34

disease predation availability of food

Question 35

name the sections of this chart showing growth in an environment with limited resources

Answer 35

Question 36

describe the ag phase in population growth

Answer 36

the organisms are adjusting to their environment

Question 37

describe the log phase in population growth

Answer 37

the growth of the population is increasing at a fast rate

Question 38

describe the stationary phase in population growth

Answer 38

the amount of births and deaths are equal

Question 39

describe the death phase in population growth in an environment with limited resources

Answer 39

once the resources begin to be used up, organisms begin to compete for resources and organisms will die as resources become scarce

Question 40

state 4 implications of a rapidly increasing population size

Answer 40

- more land needed for living - greater demands on healthcare - greater demands on education - more resources needed which puts pressure on the environment