Unit 6.2 - Populations and communities

Question 1

Sampling

Answer 1

A method of investigating the abundance and distribution of populations

Question 2

Random Sampling

Answer 2

Carried out to ensure: Representation - it is important that all individuals in a location can be selected for sampling, Removal of biases, Generalisation - allows scientists to generalise data from samples to a larger habitat

Question 3

Sampling Error

Answer 3

The difference between an estimated population size and the true population size

Question 4

Quadrat

Answer 4

A square frame that is randomly placed in an area to be studied to provide a sample

Question 5

Sessile

Answer 5

not free-moving

Question 6

Standard Deviation

Answer 6

Used to show how values are spread above and below the mean

Question 7

Capture-Mark-Release-Recapture

Answer 7

Is a method of estimating the population size of a motile species

Question 8

Lincoln Index

Answer 8

The formula for this estimated population: M*(N/R)

Question 9

Carrying Capacity

Answer 9

The maximum population size of a species that can be supported long term in an environment

Question 10

Density-Dependent Factors

Answer 10

Cause a population’s growth to change due to population density. They tend to be biotic and typically as the population increases, density dependent factors will decrease populations back to carrying capacity

Question 11

Population Density

Answer 11

The number of individuals within a given area

Question 12

Disease

Answer 12

A biotic factor, affecting population density

Question 13

Natality

Answer 13

The birth rate for a population

Question 14

Mortality

Answer 14

The death rate of a population

Question 15

Immigration

Answer 15

New individuals entering a population

Question 16

Emigration

Answer 16

The individuals leaving a population

Question 17

Exponential Growth

Answer 17

Is observed in an environment with limited competition for resources

Question 18

Sigmoid Population Growth Curve

Answer 18

When a species enters a new location, the population typically produces a Sigmoid population growth curve. Featuring, an exponential phase, transitional phase and plateau phase

Question 19

Interspecific Relationships

Answer 19

Relationships between members of different species

Question 20

Interspecific Competition

Answer 20

Occurs when individuals from different species compete with each other for the same resources

Question 21

Parasitism

Answer 21

Is a form of symbiosis where one species benefits, but the other species is harmed

Question 22

Pathogenicity

Answer 22

Occurs when an organism infects another species, causing a disease

Question 23

Root Nodules

Answer 23

Plants in the legume family, including soybeans, have nodules containing nitrogen-fixing bacteria. Plants require nitrogen compounds, but are unable to synthesise these compounds. These nitrogen fixing bacteria provide the plant with a supply of nitrogen compounds. The bacteria recieves carbohydrates and other organic compounds, produced by photosynthesis, from the plant.

Question 24

Mycorrhizae

Answer 24

Are formed by a symbiotic relationship between the roots of a plant and a fungus. e.g orchids

Question 25

Zooxanthellae

Answer 25

Zooxanthellae algae have a mutualistic relationship with coral polyps. The zooxanthellae produce nutrients such as glucose used by the corals, as well as removing wastes and producing oxygen. The coral polyps provide protection and carbon dioxide for the zooxanthellae.

Question 26

Endemic Species

Answer 26

Native species

Question 27

Invasive Species

Answer 27

Often replace endemic species by competitive exclusion

Question 28

Alien Species

Answer 28

Are organisms that have been introduced into an ecosystem, and do not occur there naturally. Alien species become invasive species if they cause harm to the natural ecosystem

Question 29

Hypothesis

Answer 29

A proposed relationship between two or more variables that can be tested by experiment

Question 30

Test of Association

Answer 30

Tests to determine if there is a relationship between two species or between a species and an abiotic factor in an ecosystem

Question 31

Chi-Squared Test of Association

Answer 31

Carried to determine if data collected suggests whether two species in an ecosystem are associated with each other

Question 32

Predator-Prey Cycle

Answer 32

Cycles in which predator and prey populations control each other e.g with Lynxes and snowshoe hares. When prey populations are high, there is a plentiful supply of food for predators and the predator population increases too, however this causes the prey population to decrease which then results in less food supplies and the predator population decreases again. The cycle continues, creating predator-prey cycles

Question 33

Top-Down Control

Answer 33

Pressures applied at higher trophic levels to control dynamics in an ecosystem. The top predator prevents overpopulation of its prey which has an impact on many species within the ecosystem

Question 34

Bottom-Up Control

Answer 34

Are resources available to producers, affecting the growth rate of producers. Population growth at higher trophic levels is impacted by the availability of producers.

Question 35

Allelopathy

Answer 35

Is the release of chemicals by one organism which influences the germination, growth, survival or reproduction of another organism

Question 36

Antibiotic

Answer 36

Inhibits the growth of fungus, reducing the competition for resources by inhibiting the growth of bacteria near the fungus