Populations

Question 1

What is a population?

Answer 1

a group of individuals of one species
occupying the same habitat

Question 2

What method can be used to determine the mean percentage cover of a species?

Answer 2

Random number generator
use a large number of quadrats
divide total percentage by number of quadrats

Question 3

What is a community?

Answer 3

all the populations of different species occupying the same habitat at the same time

Question 4

What is a niche?

Answer 4

how an organism fits into an environment
no two species can occupy the same niche

Question 5

What determines the population size?

Answer 5

carrying capacity
- the max size a habitat can support

Question 6

What is the standard population curve?

Answer 6

increases and enough resources
starts to level off as increased competition

Question 7

What are some abiotic factors?

Answer 7

temp, light intensity, pH, water, humidity

Question 8

Why does temp affect growth?

Answer 8

enzymes (for photosynthesis) denature in high temps
reactions slower as less KE in low temps

Question 9

Why does light affect growth?

Answer 9

photosynthesis limited in low light

Question 10

Why does pH affect growth?

Answer 10

enzymes denature at wrong pH

Question 11

Why does water and humidity affect growth?

Answer 11

high humidity = decrease in transpiration - less water for photosynthesis
photosynthesis limited with low levels water -> used for support (turgidity)

Question 12

What are biotic factors?

Answer 12

intraspecific competition - same species
interspecific competition - different species
predation

Question 13

How can the size of a population be estimated?

Answer 13

mark-release-recapture for motile organisms

Question 14

What are the limitations and assumptions for mark-release-recapture?

Answer 14

‘mark’ isn’t lost
no births/deaths
no immigration/migration
equally likely to get caught

Question 15

how do you calculate pop. size after mark-release-recapture?

Answer 15

no. in 1st sample x no. in 2nd sample / no. in 2nd sample marked

Question 16

What is an abiotic factor?

Answer 16

non-living factor of environment

Question 17

Describe mark-release-recapture

Answer 17

capture, count, release
mark carefully to avoid detection
recapture, count marked and unmarked

Question 18

What is spearmans rank?

Answer 18

use when two sets of numerical data may be correlated
values must be paired so their ranks can be compared
must be enough data to make judgement (10-15)

Question 19

What does it mean if the test value> critical values?

Answer 19

probability that difference in… was due to chance is less than (p value)
so reject null hypothesis

Question 20

What does it mean if the test value< critical values?

Answer 20

probability that the difference in… was due to chance is more than (p value)
so accept null hypothesis

Question 21

What is uniformly distributed?

Answer 21

organisms evenly spread between regions

Question 22

How do the assumptions for proportional sampling differ from mark-release-recapture?

Answer 22

suggest organisms are evenly distributed
mark suggests size of total area not required

Question 23

How are the assumptions for proportional sampling and mark-release-recapture the same?

Answer 23

animals are apart of same population

Question 24

What information do standard deviations give?

Answer 24

values spread around mean

Question 25

What is an ecosystem?

Answer 25

a collection of communities an their non-living surroundings, which form a stable, self-perpetuating system

Question 26

How can you estimate the population of motile organisms?

Answer 26

Mark-release-recapture

Question 27

How do you measure a population in a uniform area?

Answer 27

Create a grid using two 10m tape measures Use quadrants with random sampling by using a random sampling generator

Question 28

How do you measure a population along an environmental gradient?

Answer 28

Transect with systematic sampling

Question 29

What are saprotrophs?

Answer 29

Secrete digestive enzymes onto dead matter to break down

Question 30

What is succession?

Answer 30

Changes, over time, of the species which occupy a particular area

Question 31

What are pioneer species?

Answer 31

E.g. moss/lichen Asexual reproduction Photosynthesise Ability to fix nitrogen from atmosphere Tolerance to extreme conditions Rapid germination of seeds

Question 32

Why is it good that pioneer species asexually reproduce?

Answer 32

Quicker to reproduce so can create a large population

Question 33

What happens after the pioneer species?

Answer 33

Lichen die and decompose Release sufficient nutrients to support community Organic matter builds up Mosses//small fern starts to grow They die and decompose This makes conditions less hostile

Question 34

What happens after the decomposition of pioneer species?

Answer 34

Topsoil/humus becomes more fertile Small plants can grow Die and decompose Leaves organic matter that helps retain water and provide anchorage for roots

Question 35

How is a stable climax community reached?

Answer 35

More plants grow and decompose Abiotic conditions become less hostile Greater variety of habitats/niches Increased biodiversity More complex food webs Increased biomass

Question 36

What is primary succession?

Answer 36

From purely inorganic starting point E.g. sand dune/bare rock

Question 37

What is secondary succession?

Answer 37

From area cleared of organisms but with soil present E.g. land cleared after fire

Question 38

What does a sand dune ecosystem show?

Answer 38

Succession over a distance

Question 39

What is a plagioclimax community?

Answer 39

A community that will not develop further as humans are influencing it E.g. heathland

Question 40

How is a plagioclimax community held at this intermediate stage of succession?

Answer 40

Mowing, grazing

Question 41

What would happen if the processes stopped in a plagioclimax community?

Answer 41

Succession would continue and the area would become a woodland

Question 42

What is conservation?

Answer 42

Reversing impacts on environment Often involves managing succession to prevent a climax community being achieved (deflected succession) Pioneer species would be outcompeted if not

Question 43

What are the types of conservation?

Answer 43

Managing succession Rewilding Conservation areas Laws on hinting/fishing Increasing habitats/niches

Question 44

What are the personal reasons for succession?

Answer 44

Recreation Health and wellbeing

Question 45

What are the ethical reasons for conservation?

Answer 45

Species right for habitats Decrease extinction

Question 46

What are the economic reasons for conservation?

Answer 46

More tourism More resources e.g. medicine from plants

Question 47

What are the cultural/aesthetic reasons for conservation?

Answer 47

Inspirational for writers/poets/artists Heritage

Question 48

Why do species present change during succession?

Answer 48

Pioneer species are outcompeted by larger species species change the environment

Question 49

How does succession result in the formation of a forest?

Answer 49

Pioneer species grow on barren land then decompose to create organic matter More species can grow on land making it less hostile as soil can’t hold more water Conditions further change to favour trees and soil becomes deep enough to hold roots