Unit 19 - Organisms and their environment

Question 1

Forms of energy passing through organisms

Answer 1

Light energy from sun –> chemical energy

Question 2

Energy lost in flow

Answer 2

heat energy + activities and processes e.g. growth

Question 3

Process which energy is transferred by

Answer 3

Ingestion

Question 4

Food chain

Answer 4

Shows the direction of energy from one organism to the next

Question 5

Consumers

Answer 5

Organisms that get their energy by feeding on other organisms

Question 6

Producer

Answer 6

An organism that makes its own organic nutrients usually from sunlight

Question 7

Herbivores

Answer 7

Animals that get their energy by eating plants

Question 8

Carnivores

Answer 8

Animals that get their energy by eating other animals

Question 9

Decomposers

Answer 9

Organisms that get their energy from dead or waste organic material

Question 10

Types of consumers

Answer 10

• Primary
• Secondary
• Tertiary …
• Depending on place in the food chain

Question 11

Food web

Answer 11

A network of interconnected food chains to show multiple pathways of energy flow through an ecosystem

Question 12

Overharvesting

Answer 12

Harvesting something excessively to a point that it gets depleted

Question 13

Foreign species

Answer 13

A species not found naturally in an ecosystem

Question 14

Trophic levels

Answer 14

Represent levels of energy transfer

Question 15

Biomass of an organism

Answer 15

The total mass of an organism’s living material

Question 16

Unit for biomass

Answer 16

g/m^2

Question 17

Reasons why only 10% of available energy is transferred

Answer 17

• Not all the plant is eaten
• Energy is used to make inedible tissue
• Energy is lost as heat during respiration
• Energy lost as heat
• Energy lost as excretory products
• Energy used for biological activities

Question 17

How carbon dioxide is removed from air

Answer 17

Photosynthesis - carbon dioxide becomes carbohydrates

Question 18

Carbon in feeding

Answer 18

• Carbon is passed in compounds when feeding
• Proof is fossil fuels

Question 19

How carbon dioxide returns into air

Answer 19

• Respiration
• Combustion

Question 20

Four main carbon reservoirs

Answer 20

• Atmosphere
• Oceans
• Land biomass
• Fossil fuels

Question 21

Processes involved in the carbon cycle

Answer 21

• Change to ecosystems - cutting down forests adds carbon dioxide to the air
• Fossil fuels - burning of fossil fuels adds carbon dioxide to the air
• Ocean/atmosphere - more carbon dioxide gas dissolves in the ocean than that that escapes into the air
• Respiration/photosynthesis - takes more carbon dioxide out of the air than that released by respiration & decomposition
• Rocks - Manufacturing of cement changes carbon in rocks to carbon dioxide

Question 22

Uses of nitrogen

Answer 22

• Air
• Liquid nitrogen
• Amino acids & proteins
• Substances that organisms can use e.g. nitrate ions

Question 23

Nitrogen fixation

Answer 23

Converting atmospheric nitrogen into substances that plants can absorb e.g. nitrates

Question 24

Two methods of nitrogen fixation

Answer 24

• Lightning - nitrogen gas molecules combine with oxygen gas in the air to make nitrogen oxides that dissolve in rainwater and are washed into the soil
• Bacteria - bacteria live freely in soil and convert nitrogen gas in the air to ammonia

Question 25

Denitrification

Answer 25

Converting nitrate ions into atmospheric nitrogen

Question 26

Nitrification

Answer 26

Ammonium ions in the soil are converted to nitrate ions
- NH^4+ –> NO2 –> NO3

Question 27

How nitrogen is returned to the environment from animals and plants

Answer 27

• Deamination in animals - nitrogen containing part of amino acids comes urea and is excreted
• Decomposition - decomposers break down plant and animal proteins and waste to make ammonium ions

Question 28

Population

Answer 28

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

Question 29

Community

Answer 29

Consists of all of the populations of different species in an ecosystem

Question 30

Ecosystem

Answer 30

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

Question 31

Factors that affect population size

Answer 31

• Food supply - increase food leads to increase, lack leads to decrease
• Predation - if predation is faster than breeding population decreases, fewer prey leads to less predators
• Disease - Reduce population sizes quickly
• Competition -

Question 32

Four factors that determine how size of population changes

Answer 32

• Number of births
• Immigration
• Number of deaths
• Emigration

Question 33

Stages of the sigmoid curve of population growth

Answer 33

• Lag phase - slow increase in population size when introduced to new environment
• Exponential (log) phase - resources are relatively plentiful - individuals reproduce at a high rate - exponential increase
• Stationary phase - resources are limited, population is at the carrying capacity of the environment, competition for resources
• Death phase - Rapid decrease in population caused by a change in the environment

Question 34

Limiting factor / environmental resistance factors

Answer 34

Something that keeps a population from increasing in size

Question 35

Carrying capacity

Answer 35

The maximum number of organisms that an ecosystem can support