Definitions

Question 1

Lag phase

Answer 1

• very slow increase in the number of organisms
• due to the time needed to adapt to the environment
• may involve nutrient assimilation (making appropriate enzymes to digest food), egg production, egg and larval development, gestation period (in mammals)

Question 2

Exponential phase

Answer 2

• population numbers increase by the same factor in each time unit
• reproduction creates new members of the population which add to the population’s reproductive capacity (ability to reproduce)
• there is little competition since there are sufficient resources
• the numbers increase by a value called the intrinsic rate of natural increase and the population is illustrating its biotic potential

Question 3

Biotic potential

Answer 3

The maximum reproductive potential (rate) of a population living under optimum/ideal environment conditions

Question 4

Stationary (stable) phase

Answer 4

• population numbers remain relatively stable
• for all populations can’t continue indefinitely
• environmental resistance
• as population numbers increase resources become limiting, competition increase and there may be an accumulation of waste
• there is a decline in birth rate combined with an increase in death rate so that recruits is equal with losses
• the population reaches its carrying capacity

Question 5

Environmental resistance

Answer 5

• the environmental factors that eventually stop population growth (prevent the population from remaining at its biotic potential)
• e.g. competition, disease, predation, and an unfavourable climate

Question 6

Carrying capacity

Answer 6

• the maximum population number that an environment can support under a particular set of conditions.
• this is very much determined by the resources available e.g. food

Question 7

Decline phase

Answer 7

• population numbers decrease rapidly
• the population has exhausted the resources and/or there is an accumulation of toxic waste so the the birth rate falls to zero and the death rate increases
• population numbers crash

Question 8

Biotic factors

Answer 8

Organisms are affected by the other organisms of the same or different species e.g. food supply or predation

Question 9

Abiotic factors

Answer 9

Organisms are dependent upon the physical and chemical factors (non-living) that make up their environment e.g. climatic and edaphic factors

Question 10

Climatic factors

Answer 10

Light intensity
Temperature
Rainfall
Wind
Water currents

Question 11

Edaphic factors and other factors

Answer 11

pH
Moisture
Mineral availability
Texture

Oxygen and carbon dioxide concentration

Question 12

Renewable resource

Answer 12

Resources are continually being replaced and made available to the organism e.g. trees continually fall in woodland and provide food for wood lice
The populations tend to remain in its stationary phase

Question 13

Non-renewable resource

Answer 13

Resources are initially available but not replaced e.g. yeast grown in a laboratory batch cu,true will eventually run out of nutrients. The populations will have an exponential phase followed by rapid decline as the resources are consumed

Question 14

Interspecific competition

Answer 14

Occurs when two different species require a common resource which is in limited supply

Question 15

Ecological niche

Answer 15

The role of an organism in the ecosystem (what it feeds on, nutrient needs, competition with other organisms, it’s temperature, water, etc)

Question 16

Competitive exclusion principle

Answer 16

Two species cannot share the same niche without species being eliminated

Question 17

R-selected species

Answer 17

Species with a high intrinsic capacity for population increase
E.g. bacteria, insects, weeds, mice and rats

Question 18

Boom and bust population growth

Answer 18

The populations of the species increase rapidly as a resource becomes available and crash as the resource is used up, with repeated cycles of boom and bust

Question 19

K-selected species

Answer 19

These species have more stable populations and they usually remain at the carrying capacity of the environment
E.g. elephants, humans, trees

Question 20

Mutualism

Answer 20

Both species gain, interaction may be necessary for both
Effect on pop. growth : +/+

Question 21

Predation

Answer 21

The predator species gain, the prey species loses
Effect on pop. growth : +/-

Question 22

Competition

Answer 22

Both species lose while interacting, the species most affected is eliminated from its niche
Effect on pop. growth : -/-

Question 23

Grazing

Answer 23

The eating of plants by herbivorous animals

Question 24

Parasite

Answer 24

An organism that lives outside (ectoparasite) or inside (endoparasite) it’s host, benefiting from it and causing harm over an extended period of time

Question 25

Pest

Answer 25

Any organism that competes with or damages a population of plants or animals that are of economic importance to humans
E.g. weeds competing with other plants, rabbits eating crops, insects damaging plants like aphids

Question 26

Chemical control

Answer 26

Spraying with a chemical substance that kills the pest (pesticides)

Question 27

Biological control

Answer 27

Making use of another organism to kill the pest

Question 28

Parasites

Answer 28

Species whose immature stage develops on or within a single host, ultimately killing the host. Most have very narrow host range

Question 29

Pathogens

Answer 29

Disease-causing organisms including bacteria, fungi and viruses. They kill or weaken their host and are relatively specific to certain insect groups

Question 30

Predators

Answer 30

Mainly free living species that consume a large number or prey during their lifetime. E.g. ladybird beetles are used for attacking aphids because they can eat their own weight in aphid’s in a single day