Module 3

Question 1

Discuss factors that need to be considered in sampling a population to estimate its
size?

Answer 1

• Accuracy vs. precision
• Scale – size of survey area
• Replication – larger and/or more surveys may be needed for rare individuals
• Timing of important life cycle events such as mating/birth/migrating
• Life span and number of offspring, % of offpring make it to maturity.

Question 2

Explain how the exponential and logistic growth models relate to changes in
population size and structure, especially following disturbance?

Answer 2

• The exponential model describes population growth in an idealised, unlimited environment.
• The logistic model describes how a population grows more slowly as it
  nears its carrying capacity

Question 3

Three pillars of sustainability?

Answer 3

social, environmental, economic

Question 4

Define population

Answer 4

Individuals of a species living in the same general area. Often described by boundaries, sometimes by characteristics or genetic differences.
* rely on the same resources
* are influenced by similar environmental factors
* Likely interact and breed with one another

Question 5

What effects do abiotic and biotic factors have on populations?

Answer 5

affects density, dispersion and demographics of population. e.g. number of predators determine how many young offspring make it to maturity.

Question 6

What are different types of community interactions?

Answer 6

• Competition
• Predation
• Herbivory
• Mutualism
• Commensalism
• Parasitism

Question 7

Example of tropic direct and indirect effects?

Answer 7

If owls dissappear, mice numbers will increase (direct effect). but the mice feed on beetles so the beetles will decrease (indirect). and the plants the beetles fed on then increase (indirect).

Question 8

Why is it important to measure commuities?

Answer 8

e.g. for food profuction (fish stocks)
e.g. for health (bacteria in/on the body)

Question 9

What is meant by trophic cascades?

Answer 9

Networks of direct and indirect interactions that shape communities and ecosystems. Predators limit the density of their prey, enhancing survival of lower trophic groups. e.g. wolves control deer populations, in turn they don’t overgraze and destoy food sources and habitats for other species.

Question 10

What alters communities over space and time?

Answer 10

• Communities are dynamic
• Frequent disturbances such as overfishing prevent communities from reaching a balance in species diversity & composition.

Question 11

Is disturbance always bad?

Answer 11

Disturbance is not always bad. It depends on your perspective. There are winners and losers. Example: mild bush fires can be good for seeds to gain access to sunlight and germinate. the fires can also clear invasive weeds.

Question 12

What does ecological succession refer to?

Answer 12

the process of a disturbed area being colonised by pioneer species, which are gradually replaced by intermediate species, which are in turn replaced by a climax commuity.

Question 13

Explain how early species influence later species in ecological succession

Answer 13

How well the ecosystem responds depends on the performance of populations and interactions within the community over time.

Pioneer species may:
1. Facilitate later species – by making the
environment more favourable (e.g. food,
shelter)
2. Inhibit later species – competition for space
and resources can limit arrival and success
3. Independent of later species – later species not influenced by conditions created by early
species

Question 14

Give examples of gloval environmental changes?

Answer 14

climate change, altered disturbance regimes (e.g. fire), novel assemblages (invasives), land use changes (e.g. agriculture)

Question 15

What are scientists looking at when it comes to environmental change?

Answer 15

Chemical, biological, geological and/or physical disturbances of the oceans and land. Especially:
I. Nutrient and water cycles
II. Time scales
III. Spatial scales
IV. “anthropogenic” disturbances
V. Impacts on biodiversity and society

Question 16

What is the extent and concern of livestock?

Answer 16

Livestock biomass is greater than
human biomass and greater than all
wild mammal biomass
- Deforestation
- Land-use change
- Greenhouse gas emissions
- Water usage

Question 17

What is the threat of greenhouse gases?

Answer 17

Today’s concentration of CO2 is more than 30% higher and rising 250 times faster than at any point in the last 800,000 yrs. Caused by burning of fossil fuels and global deforestation
* In atmosphere: leads to global warming
* In water: warming + CO2 dissolves and lowers pH (“ocean acidification”)
* The RATE of change is the main threat, species need time to adapt and evolve.

Question 18

What is ‘r’ and ‘K’ and what does it have to do with adaptation?

Answer 18

Its a scale of Life History Traits.
‘r’ represents organisms that produce a large number of offspring but don’t tend to their offpring, e.g. oyster. ‘K’ is the opposite, few offspring but large care & time investment for parent(s), e.g. chimpanzee.

organisms that have longer time between generations take longer to adapt, and are more vulnerable to environmental change.

Question 19

Discuss (with examples) what features make organisms more resilient or susceptible to change?

Answer 19

• phenotypic plasticity (e.g. butterflies can change their colour depending on wet/dry season for purposies of mating or surviving)
• genetic variability (e.g. tasmanian devils low genetic diversity more suseptible to extinction from a disease)
• generalist diet: more options food sources e.g. noisy miner eats a range of things whilst bell miners have a highly specialised diet.
• niche habitat: species dependent on resticted georgapic range.