Ecology And Populations

Question 0

How are ecosystems dynamic

Answer 0

Population sizes rise or fall because the living things have interrelationships and so a change in one population affects another

Question 1

What is an ecosystem

Answer 1

A group of living organisms and non living things living together, and the relationships between them

Question 2

What’s a biotic factor

Answer 2

A living feature of an ecosystem, eg predators or availability of food

Question 3

What’s an abiotic factor

Answer 3

A non living feature of an ecosystem, eg temperature or water availability

Question 4

What’s a producer

Answer 4

An organism which produces organic molecules using light energy, eg plants

Question 5

What’s a consumer

Answer 5

An organism that eats another, eg birds, animals

Question 6

What’s a decomposer

Answer 6

An organism that feeds on waste material and dead organisms

Question 7

What’s a trophic level

Answer 7

The level at which an organism feeds

Question 8

How is energy transfer shown

Answer 8

Food chains show how energy is transferred. The arrows show the direction of energy transfer. Organisms tend to be part of multiple food chains, so this can be shown as a food web

Question 9

How can a pyramid of biomass be used to measure energy transfer

Answer 9

The area of the bar represents the dry mass of the organisms - usually ecologists just calculate this from the wet mass

Question 10

How can pyramids of energy be used to measure energy transfer

Answer 10

They show a measure of how much heat energy is produced per gram of an organism!

Question 11

What’s productivity

Answer 11

The rate at which energy passes through each trophic level

Question 12

What’s gross primary productivity

Answer 12

The rate at which plants convert light energy into chemical energy

Question 13

What’s net primary productivity

Answer 13

The amount of energ actually available to the primary consumer

Question 14

Explain why energy transfer is never 100% efficient

Answer 14

Some energy is lost at each trophic level. Living organisms carry out life processes, eg respiration. Energy remains stored in dead organisms and waste material, which is then only available to decomposes. Some parts of organisms can’t be digested by consumers

Question 15

What are the 6 ways we can improve primary productivity

Answer 15

Light, water, temperature, nutrients, pests, competition

Question 16

How can humans stop light reducing primary productivity

Answer 16

Plant crops earlier in the year to maximise natural light, or plant under light banks

Question 17

How can humans stop water reducing primary productivity

Answer 17

Irrigate crops, drought resistant crops eg wheat in Australia

Question 18

How can humans stop temperature reducing primary productivity

Answer 18

Planting earlier to increase the growing season before its too cold to grow crops

Question 19

How can humans stop nutrients reducing primary productivity

Answer 19

Crop rotation, including nitrogen fixing plants eg peas and beans, fertilising the soil

Question 20

How can humans stop pests reducing primary productivity

Answer 20

Pesticides, pest resistant crops

Question 21

How can humans stop competition reducing primary productivity

Answer 21

Use herbicides to limit competition from weeds

Question 22

What are the 5 ways to improve secondary productivity, explain why for each one

Answer 22

Harvest animals before adulthood as more of the energy in the young is invested into growing. selective breeding eg faster growth rates, high milk yield. , antibiotics, to avoid energy loss to pathogens or parasites. no grazing to avoid loss of energy through movement, heating so energy isn’t used to regulate body temperature

Question 23

Define primary succession

Answer 23

The development of a community from bare ground

Question 24

Describe an example of primary succession

Answer 24

Surtsey, Iceland. Formed in 1960 by a volcanic eruption. Algae and lichens begin to live on bare rock - pioneer community. Erosion of rock, build up of dead organisms produces enough soil for mosses and ferns which replace the pioneer community. Similarly, larger plants succeed these until a final stable community is reached, called a climax community

Question 25

How can quadrats measure distribution and abundance

Answer 25

Can record distribution, presence of a species, or abundance, number of a species or percentage cover

Question 26

How do we use a quadrat

Answer 26

Take samples from a range of areas to reduce bias. Use a cumulative frequency graph to tell you how many samples you need to use. Population size of a species is average number of individuals in a species divided by the fraction of total habitat area

Question 27

How can we use a transept to measure distribution and abundance

Answer 27

It’s a line taken across a habitat. Sample regular intervals along the line. Line transect is which species is touching the tape and belt transect is where you place a quadrat next to the line, can be interrupted or continuous

Question 28

Describe the role of decomposers

Answer 28

Bacteria and fungi are saprotrophic which means they secrete enzymes onto dead/waste material, these enzymes digest the material into small molecules, which are absorbed by the organism and respired to produce energy

Question 29

Describe nitrogen fixation

Answer 29

Can occur through haber process and lightning but most occur due to nitrogen fixing bacteria. Many live in the soil and fix nitrogen gas within it, some such as rhizobium live in the roots of peas and beams. Mutualistic relationship as bacteria give fixed nitrogen and recieve glucose in return. The bacteria use an enzyme, nitrogen reductive, to reduce nitrogen has to ammonium ions used by the host plant.

Question 30

Describe nitrification

Answer 30

Happens when chemoautotrophic bacteria in the soil absorb ammonium ions which are released by bacteria. Chemoautotrophic bacteria get their energy by oxidising ammonium ions to nitrates, eg nitrosomonas bacteria, or by oxidising nitrites to nitrates, nitrobacter bacteria

Question 31

What does rhizobium bacteria do

Answer 31

Live in the roots of peas and beans and fix nitrogen

Question 32

What does nitrosomonas bacteria do

Answer 32

Oxidise ammonium ions to produce nitrates

Question 33

What does nitrobacter bacteria do

Answer 33

Oxidise nitrites to form nitrates

Question 34

Describe denitrification

Answer 34

Conversion of nitrates back to nitrogen gas, when bacteria are grown without oxygen eg in waterlogged soil, they use nitrates as a source of oxygen for their respiration and produce nitrogen gas and nitrous oxide

Question 35

Define carrying capacity

Answer 35

The maximum population size that can be maintained over a period of time in a particular habitat

Question 36

Define intraspecific competition

Answer 36

Competition between individuals of the same species, resources become limiting so the best adapted individuals survive to reproduce

Question 37

Define interspecific competition

Answer 37

Happens between individuals of different species, and affects both population size and species distribution

Question 38

What are the three phases of population growth

Answer 38

Lag phase - only a few individuals so reproduction rate is low. Log phase - resources plentiful, rate of population growth is fast. Stationary phase - population size levelled out at carrying capacity, population fairly stable but fluctuates slightly due to environmental factors

Question 39

Give examples of limiting factors

Answer 39

Food, shelter, water, light, oxygen, shelter, nesting spaces, predators

Question 40

Describe the 5 stages of predator prey relationships

Answer 40

1. When the predator population increases, more prey are eaten. 2. The prey population get smaller, so there’s less food for the predators. 3. Fewer predators can survive so their population size decreases. 4. Prey population increases as less are eaten. 5. With more prey, predator population increases again and the cycle starts again.

Question 41

Define conservation

Answer 41

Involves the maintainence of biodiversity, and maintaining a varie of habitats and ecosystems

Question 42

Define preservation

Answer 42

protecting areas of land, unused by humans, in their untouched form

Question 43

Describe small scale timber management

Answer 43

Coppicing, pollarding which is similar but higher up so deer don’t eat the new shoots. Rotational coppicing often used to supply of timber every year. Standards are trees left to grow larger to meet demands for larger pieces of timber

Question 44

Describe large scale timber management

Answer 44

Clear felling no longer done as reduced soil mineral levels, destroyed habitat and soil erosion leading to river pollution. Selective cutting leaves each area fairly unaffected. If each tree produces more wood, less trees will need to be cut down to meet timber demands. To achieve this plant tree species where they’ll grow well. Control pests and pathogens. Position trees optimally

Question 45

What are the three principles of modern sustainable forestry

Answer 45

Any tree harvested must be replaced. Must maintain biodiversity and natural cycles. Locals should benefit from the forest.

Question 46

Describe ethical reasons for conservation

Answer 46

Every living thing has a right to survive. We are ethically responsible for conserving species

Question 47

Describe economic reasons for conservation

Answer 47

Indirect value, eg insects polluting crops helps farmers. Direct benefit eg harvesting fur or meat etc

Question 48

Describe social reasons for conservation

Answer 48

Provide a valuable food source. Benefits to medicine. Allows for recreation eg hiking or birdwatching or both simultaneously

Question 49

Why is conservation dynamic

Answer 49

It changes with the needs of the environment or species in question. It uses management and sometimes involves reclamation of land for habitats

Question 50

Describe habitat disturbance in the galapagos

Answer 50

Oil spill in 2001 harmed marine and coastal ecosystems increased pollution, building, conversion of land for agriculture has destroyed habitats, forests of Salesia trees destroyed for this use

Question 51

Describe over exploitation in the galapagos

Answer 51

200,000 tortoises killed in 50 years and made the pinta tortoise extinct. Fishing has left populations depleted and over 150,000 sharks killed for their fins including 14 species listed as endangered

Question 52

Describe introduced species in the Galapagos

Answer 52

Red quinine trees introduced and eradicated cacaotillo shrubs. Goats outcompete tortoises for grazing and turn forests into grassland, leading to soil erosion.

Question 53

Describe the preventative methods introduced in the Galapagos to minimise the effect of introduced species

Answer 53

Quarantine system, tourists searched for foreign species. Culling, eg feral pigs and feral goatees. 40% coastal zones allow no extraction of resources