Topic 7C: Populations in Ecosystems

Question 1

What is a niche?

Answer 1

• The role of a species within its habitat

Question 2

How are niches occupied?

Answer 2

• Can only be occupies by one species
• If occupied by 2 - one outcompetes the other and is more successful

Question 3

What does a niche include?

Answer 3

• Biotic interactions - what it eats and is eaten by
• Abiotic interactions - O2 in and CO2 out

Question 4

What is an adaptation?

Answer 4

• Features that increase an organism’s chance for survival
• More likely to reproduce and pass on allele for adaptation

Question 5

What are three types of adaptation?

Answer 5

• Physiological - processes inside a body
• Behavioural - the way an organism acts
• Anatomical - structural features on the body

Question 6

What are three examples of adaptations to abiotic conditions?

Answer 6

• Otters - webbed paws - can live in water and on land
• Seals - blubber - stay warm and survive
• Hedgehogs - hibernate - conserve energy to survive by reducing metabolic rate

Question 7

What are three examples of adaptations to biotic conditions?

Answer 7

• Otters - use rocks to smash open seafood - access to other food sources
• Frogs - mating calls - attract same species - reproduce successfully
• Bacteria - can produce antibiotics - kills others to reduce competition

Question 8

What is carrying capacity?

Answer 8

• Maximum stable population size of a species that an ecosystem can support

Question 9

How can abiotic factors cause variation in population size?

Answer 9

• When ideal –> organisms can grow and reproduce well - ideal temp (less energy needed to maintain temp) etc
• When not ideal –> cannot grow and reproduce well

Question 10

What is interspecific competition and how does it cause populations to vary?

Answer 10

• Different species, same resources
• If one is better adapted, it will outcompete the other

Question 11

Define intraspecific competition and how it causes population size variation

Answer 11

• Same species, same resources
• Cyclical –> plentiful resources, pop inc, resources become limited, pop reduces, resources become more plentiful again

Question 12

How does predation affect population sizes?

Answer 12

• Prey population increases - more food for predator
• Predator population increases - eats more
• Prey population decreases - less food available
• Predator population decreases again

Question 13

How do you take a random sample in an area?

Answer 13

• Choose a small sample area and split it into a grid
• Randomly generate coordinates - repeat lots
• Can multiply mean up to the whole area

Question 14

What are quadrats and what are they used for?

Answer 14

• Square frame divided by strings into 100 small squares
• Investigate non motile (plants) & slow moving (limpets)
• Measure species frequency or number of individuals
• Measure % cover - count all squares over 1/2 covered

Question 15

How are transects used?

Answer 15

• Finding distribution across an area
• Belt –> quadrats placed next to each other - find frequency and % cover
• Interrupted belt –> placed at intervals to cover larger distance

Question 16

What is mark - release - recapture for?

Answer 16

• Measures the abundance of motile species

Question 17

Describe the process of mark - release - recapture

Answer 17

• Capture a sample - use pitfall trap
• Mark harmlessly - paint
• Release and wait a week
• Take a second sample and count those with marks

Question 18

What is the equation for finding total population size from mark - release - recapture?

Answer 18

total pop size = (no/ in 1st sample x no/ in 2nd sample) / number marked in 2nd sample

Question 19

What assumptions are made during mark - release - recapture?

Answer 19

• Organisms have enough time to mix back into the population
• Marking doesn’t change their chances of survival
• The marking is still visible
• There were no changes to population size during the experiment

Question 20

How would you investigate an environmental factor with species distribution?

Answer 20

• Along a transect - measure something else e.g. pH
• Can plot % cover and pH together - same graph
• Can compare

Question 21

In investigations, what ethical considerations must be made?

Answer 21

• Needs to have the smallest possible impact on the environment
• Restrict where people can walk and avoid treading on plants

Question 22

What safety measures need to be taken during these investigation?

Answer 22

• Sea - do at low tide
• Wear suitable clothes
• Wash hands after

Question 23

What is succession?

Answer 23

• How an ecosystem changes over time

Question 24

How does primary succession work?

Answer 24

• On newly formed / exposed land
• Pioneer species - specially adapted
• Changes the abiotic conditions - produces soil by decomposing - makes environment less hostile
• New organisms with different adaptations arise - increased biodiversity
• New species can change the environment so it is no longer suitable for the pioneer species

Question 25

Describe secondary succession

Answer 25

• An area of cleared plants but soil remains
• Succession starts at a later stage
• Pioneer species is larger plants
• At each stage new and better adapted organisms for the improved conditions outcompete old - dominant species
• Ecosystem = more complex - new species move in alongside - increases biodiversity

Question 26

What is a climax community?

Answer 26

• The largest and most complex community if plants and animals the ecosystem can support
• Lives in a steady state

Question 27

How are climax communities different in different climates?

Answer 27

• Temperate climate –> water available, mild temp, minimal changes - large tress, deep soils
• Polar climate –> minimal water, low temp, large seasonal changes - no large trees, just shrubs

Question 28

What is conservation?

Answer 28

• Protection and management of species and habitats in a sustainable way

Question 29

What is a plagioclimax?

Answer 29

• Humans prevent succession to stop a true climax community from forming
• Mowing a lawn prevents other plants from growing

Question 30

Describe conservation by preventing succession

Answer 30

• Maintains habitats for native species and prevents eradication
• Allow animals to graze - keeps plants low + from taking over
• Managed fires - stimulates secondary succession - pioneer species are the one being conserved

Question 31

How do humans and conservation conflict?
Use grassland as an example

Answer 31

• People want to raise cattle for income
• These can destroy the land for wildlife
• Conservationists help them to make money from conservation and to farm sustainably
• Meets current economic needs and sustains life

Question 32

What are 4 other conservation methods?

Answer 32

• Seedbanks
• Fishing quotas
• Protected areas
• Breeding endangered species in captivity