3.3.1 The Effect of Biotic and Abiotic Factors on Populations Flashcards Preview

A-level Biology Oxford AQA > 3.3.1 The Effect of Biotic and Abiotic Factors on Populations > Flashcards

Flashcards in 3.3.1 The Effect of Biotic and Abiotic Factors on Populations Deck (61)
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1

Define Habitat

Place where an organism lives

2

Define Population

All the organisms of one species in a habitat

3

Define Community 

All populations of different species in a habitat = community

4

Define Ecosystem

A community + all abiotic & biotic factors in the area

5

Define Abiotic conditions

Non-living features of ecosystem

e.g. temperature, availability of water

6

Define Biotic conditions

Living features of ecosystem

e.g. predators, food

7

Define Niche

Role of a species within its habitat

e.g. what it eats, where and when it feeds

8

Define Adaptation

Feature that member of a species have that increases their chance of survival and reproduction

9

The niche of a species occupies within its habitat includes...

  • Its biotic interactions 
    • e.g. the organisms it eats, and those it's eaten by
  • Its abiotic interactions 
    • e.g. oxygen an organism breathes in & CO2 it breathes out

10

If 2 species try to occupy same niche, there'll be ______

competition

(One species will be more successful & it'll be one its own)

11

Organisms are adapted to both ____ conditions (e.g. water availability) and _____ conditions (e.g. predators) in their ecosystem 

Organisms are adapted to both abiotic conditions (e.g. water availability) and biotic conditions (e.g. predators) in their ecosystem 

12

What is meant by carrying capacity?

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

13

What does population size vary due to? (2x)

  • Abiotic Factors 
  • Biotic Factors 

14

Name 3 examples of abiotic factors 

light, water, space available, temperature, chemical composition of surroundings, pH, etc.

15

Explain how when a mammal's surroundings is the ideal temperature (e.g. abiotic factor), it can lead variations in population size

  • e.g. when temperature of a mammal's surroundings is the ideal temp. for metabolic reactions to take place = don't have to use up as much energy maintaining their body temperature 
  • ∴ more energy can be used for growth and reproduction & population size will increase

16

Name 3 biotic factors that affect population size

  • Intraspecific Competition 
  • Interspecific Competition 
  • Predation 

17

What is interspecific competition?

When organisms of different species compete for same resources

18

Explain how interspecific competition can cause a change in population size 

  • Results in reducing the resources available to both populations
    • e.g. if share same food source = less available for both of them
    • Both populations limited by lower amount of food
    • Less energy for growth and reproduction
    • ∴ populations sizes lower for both species

19

What happens when 2 species are competing but one is better adapted to surroundings?

Less adapted species = out-competed (won't exist with other species)

20

Define Intraspecific Competition

When organisms of the same species compete for same resources

21

Explain how intraspecific competition leads to variation in population size

  1. Population of species increases when resources plentiful
    • Population ↑ = more organisms competing for same amount of space + food
  2.  Resources become limiting (not enough for all organisms)
    • Population ↓
  3. Smaller population = less competition = better for growth and reproduction
    • Population ↑

22

Explain how predation leads to variation in population size

  1. Predator population peaks after prey population
  2. Prey population ↑ (due to less preadators/more food available)
  3. More food available = predator population ↑
  4. As predator population ↑, ↑ predation ∴ prey population ↓
  5. Less food for predators = predator population ↓

23

Predator and Prey Population Cycle

Why does the prey population initially decline?

∵ there's too many of them for amount of food available

(This is then accelerated by predation)

24

Describe how to take a random sample from an area you're investigating

  1. Choose an area to sample
  2. Samples should be random to avoid bias
    • e.g. divide field into grid and use random number generator to select coordinates
  3. Use appropriate technique to take sample
  4. Repeat processes many times to reduce likelihood that results are due to chance
  5. No. of individuals for whole area can be estimated by taking mean of data collected in each sample & multiplying it by size of whole area

25

Name 2 methods of investigating non-motile organisms

  • Transects 
  • Quadrats

26

What is recorded in each quadrat?

Species frequency or no. of individuals of each species 

27

How can the percentage cover of a species be measured?

By counting how much of quadrat is covered by species

Count a square if it's more than half-covered

28

What is the benefit of measuring percentage cover?

Quick way of investigating populations & don't have to count all individual organisms

29

What are transects used for?

Used to find out how organisms (e.g. plants) are distributed across an area

30

Describe how you would conduct a belt transect

Place quadrats are next to each other along a transect to work out the species frequency & percentage cover along transect

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