7 Genetics & Ecosystems- Populations in Ecosystems

Question 1

What is a habitat and how does this vary between species?

Answer 1

-Where an organism lives
-Diff individuals within species tend to occupy same type of habitat; individuals in diff species= more likely to occupy diff habitat but many species can occupy the same habitat

Question 2

What are the components of an ecosystem?

Answer 2

-Many individuals of same species occupy same habitat—> population
-Multiple populations of diff species in same habitat form a community
-A community & abiotic conditions (e.g. climate) in environment together form an ecosystem
-Can be big or small

Question 3

What is the difference between abiotic and biotic conditions?

Answer 3

-Abiotic; non-living environmental factors, eg climate
-Biotic; living environmental factors, eg predation

Question 4

What is a niche and how is this seen in a species?

Answer 4

-The specific role a species has in an ecosystem
-Every species has evolved to occupy only one niche & two different species cant overlap in this niche

Question 5

What are adaptations and when is an individual said to be adaptive?

Answer 5

-The characteristics of an individual that help it survive & reproduce
-If an individual is well-suited to surviving in its ecosystem—> said to be adaptive

Question 6

What are the different types of adaptations? + examples

Answer 6

-Behavioural (e.g. bird of displays its wings & ‘dances’ to attract a mate).
-Anatomical (e.g. pelicans have a pouch-like beak which allows them to scoop fish from water).
-Physiological (e.g. bears have special fat cells that release heat during hibernation).

Question 7

What is exponential growth and where is it possible?

Answer 7

-The continuous growth in population size
-Only possible where there’s an infinite supply of resources; not the case in a real ecosystem

Question 8

How are limited resources in an ecosystem significant and what is the carrying capacity?

Answer 8

-Limited supply of resources in ecosystems; individuals competing to use these
-Species w/ adaptations that allow them to gain resources better than other species= more likely to reproduce
-Reproduction causes size of population to increase
-Populations can’t increase to an infinite size due to limited resources
-Maximum size a population can maintain for long period of time= carrying capacity

Question 9

How do abiotic factors influence the carrying capacity of a species?

Answer 9

-Promoting growth; abiotic conditions are favourable for the species so more of population reproduce
-Slowing growth; abiotic conditions are unfavourable for species so less of population reproduce

Question 10

How do biotic factors influence carrying capacity?

Answer 10

-Interspecific competition; can reduce amount of resources available= slows rate of population growth
-Out-competing; When two species compete for same resource, one of them can out-compete the other if it’s more well-adapted to environment than the other & is better at gaining resources & reproducing. Out-competing allows one species to increase in population size, causes other species to decrease in population size.
-Intraspecific competition; causes fluctuations in population size
-Predation; predators & prey interact to influence each other’s population size

Question 11

How can the population of immobile/slow-moving organisms be estimated?

Answer 11

Random samples of quadrants

Question 12

What are transects and when are they used?

Answer 12

-Quadrats could also be placed at regular intervals along a transect; a line across a habitat, usually placed w/ tape measure
-Used when there’s a change/ gradient in abiotic conditions across habitat
-Used when looking for changes in abundance/distribution of species across environment

Question 13

What are line and belt transects, how are they used?

Answer 13

-Line transects; record species making contact w/ tape measure at regular intervals along transect
-Belt transect; uses quadrats; placed at regular intervals along transect. Abundance of diff species in quadrat can be measured by: percentage cover (estimate how much of the quadrat is covered by a particular species) frequency (count how many individuals of particular species are present in quadrat)

Question 14

What is mark-release-recapture?

Answer 14

A technique used to investigate population size of mobile organisms

Question 15

What are the steps involved in mark-release-recapture?

Answer 15

1.) Capture; small mammals can be captured w/ Sherman trap (box with trap door) & ground insects can be captured w/ pitfall trap
2.) Mark; captured animals marked in some way (e.g. tags), allows to identify which animals have already been counted & which have not
3.) Release; marked animals released back into environment, traps set up again. This allows them to mix w/ rest of population
4.) Recapture; new sample collected from traps. The unmarked individuals captured are counted, marked & released
5.) Calculate population size; number caught in 1st sample x number caught in 2nd sample/ number marked in 2nd sample

Question 16

What are the steps involved in belt transects being used to investigate effect of abiotic factors on species distribution?

Answer 16

1) Marking belt transect; belt transect is used to investigate how population size varies across environment, it should be marked along area where one environmental factor changes
2) Place quadrat; 1m² at regular intervals along belt transect, use it to identify which species are present & count percentage cover of diff species. If species covers 1/2> one square on quadrat= has 1% cover of it
3) Measure environmental factor; record how environmental factor investigated varies at each sample point along belt transect
4) Record results; plot graph showing how distribution of species correlates to environmental factor

Question 17

What is succession and what are the two types?

Answer 17

-The changes in an ecosystem over time
-Describes sequential change in species in a community over time
-Primary & secondary succession

Question 18

What makes an ecosystem dynamic?

Answer 18

-Are affected by changes in the structure & composition of the communities within them
-Can be affected by environmental disturbances (e.g. volcanoes, earthquakes)

Question 19

What is the climax community?

Answer 19

The ecosystem that results from succession

Question 20

Where does primary succession take place?

Answer 20

Newly exposed or newly formed land; colonised by living things

Question 21

Where does secondary succession take place?

Answer 21

Where part of an ecosystem is disturbed and remnants of the previous community remain

Question 22

What are the stages involved in primary succession?

Answer 22

-Pioneer species (specialised to live in harsh conditions of exposed land) are the first species to colonise the newly exposed land
-They help to break down substances on exposed land to form soil. When they die, they’re decomposed which contributes to soil formation
-Formation of soil makes environment less hostile
-New species colonise less hostile land. When they die, organic matter within species is released into soil by decomposition, composition of soil is changed. Soil= abiotic factor
-When new species colonise area, they’re also altering abiotic conditions & the environment so that pioneer species can no longer survive

Question 23

What are the stages in secondary succession?

Answer 23

-Pioneer species colonise damaged land
(tend to be larger in secondary succession)
-environment in secondary succession= more nutrient-rich than primary succession due to soil layer
-As pioneer species die, soil becomes more nutrient-rich, stable
-New species can colonise land; out-compete older species, become dominant
-As more species colonise land, complexity of ecosystem increases
-If there’s more species in ecosystem, is more biodiverse
-Ecosystem eventually reaches equilibrium point; where species composition no longer changing, resembles community that existed before it was disturbed. This is called the climax community

Question 24

What are the ways succession can be managed?

Answer 24

-Managing grasslands; many rare, protected species can be found in grasslands. W/ out management, grassland would quickly turn into shrubs, woodland by succession. Managing prevents succession.
-Management techniques; grazing: animals graze to prevent growth of vegetation. Burning: kills vegetation, allows secondary success to occur
-Managing heather moors; provide an habitat for game birds like red grouse; feed on young heather shoots & makes nesting sites in longer heather
If left to succession, heather would be unsuitable as either food/nesting sites for red grouse. Heather moorland= burnt approximately every 12 years to manage succession.

Question 25

Why is there a need for conservation?

Answer 25

-Humans pose huge threats to the biodiversity in the planet due to; population growth & resource exploitation
-Conservation helps oppose effects from humans and protects ecosystems & species within them to help prevent decreasing biodiversity

Question 26

What are some examples of methods of conservation?

Answer 26

-Protected areas (eg national parks); protect habitats
-Seedbanks; store seeds to avoid extinction
-Protected species; avoid extinction
-Fishing quotas; prevent overfishing

Question 27

Why is there a conflict between human needs and conservation?

Answer 27

-Conservation can be expensive
-Human population growth= high demand for food, space & other resources. Conservation can sometimes make meeting these demands difficult