3.5.2 People change communities

Question 1

Define the term ‘population’.

Answer 1

All the freely interbreeding individuals of the same species occupying the same place at the same time.

Question 2

Define the term ‘community’.

Answer 2

All the populations of different organisms living together and interacting in a particular place at a particular time.

Question 3

Define the term ‘ecosystem’.

Answer 3

The interaction of the community with the physical environment in a specific area.

Question 4

Define the term ‘habitat’.

Answer 4

The place where an organism normally lives.

Question 5

What is meant by ‘biodiversity’?

Answer 5

The variety of different organisms in a particular area.

Question 6

Explain what is meant by ‘ecological niche’.

Answer 6

The ecological role of a species within its community. It consists of all the environmental conditions and resources needed for the survival of a species within an ecosystem.

Question 7

What are the three things that the size of a population depend on?

Answer 7

• Birth rate
• Death rate
• Migration into and out of the population

Question 8

What are limiting factors?

Answer 8

Factors that keep the population at its carrying capacity.

Question 9

What is meant by ‘carrying capacity’?

Answer 9

The maximum population size that can be sustained by the ecosystem.

Question 10

What is meant be ‘environmental resistance’?

Answer 10

The limiting factors that determine carrying capacity.

Question 11

Name and explain the two kinds of limiting factors.

Answer 11

• Density-dependent factors have effects that depend on population density. They have a greater effect when the population is large and individuals are living close together. They are usually biotic factors such as predation and disease.
• Density-independent factors have similar effects regardless of the population size/density. They are usually abiotic factors such as temperature, rainfall, light intensity, fire etc.

Question 12

What kind of limiting factor results in competition between individuals for limited resources?

Answer 12

Density-dependent limiting factors

Question 13

Why would domesticated cats have been highly valued by the first farmers?

Answer 13

They would have hunted rodents that infested grain stores in early agricultural settlements.

Question 14

Why were pigeons originally domesticated?

Answer 14

As a source of food and fertiliser

Question 15

How can pigeons be a health risk to humans?

Answer 15

In wet weather, the accumulation of their droppings on pavements can pose hazards to pedestrians.

Question 16

How can pigeons damage the urban environment?

Answer 16

• Their droppings are acidic and can corrode brick and stonework.
• Gutters and drains can become blocked by droppings, nest material and dead birds causing overflow and water damage to buildings.
• Dead pigeons in uncovered water tanks can contaminate the water supply.

Question 17

Name the bacterium discovered in 1977 to be able to be used to introduce foreign genes into plant cells.

Answer 17

Agrobacterium tumefasciens

Question 18

State five reasons why crops might be genetically modified.

Answer 18

Any from:

• Resistance to pests
• Resistance to herbicides
• Resistance to disease
• Increased shelf life
• Improve flavour
• Increase hardiness
• Increase nutrient content
• Free from allergens

Question 19

Name the most commonly-inserted bacterial gene in GM crops, and its function.

Answer 19

Bt

It allows the crop plants to produce a toxin that kills insect pests but is harmless to humans.

Question 20

What is pharming?

Answer 20

Genetically modifying crops in order to produce drugs and vaccines.

Question 21

What is an Environmental Impact Assessment?

Answer 21

A detailed report that must be made when a new GM crop is brought to trial, reporting on the environmental impact the project would have.

Question 22

What is meant by ‘transgenic’?

Answer 22

Any organism whose genetic composition has been altered by the addition of foreign DNA.