Effect of the Environment on Organisms

Question 1

What are selection pressures?

Answer 1

Selection pressures are external agents, composed of both biotic and abiotic factors, that affect the survival and reproduction of organisms. They refer to the way that some environmental factors differentially affect the survival, and reproductive success of certain phenotypes in a population

Question 2

Define what biotic factors are. Provide 4 examples.

Answer 2

Any living factor that affects the growth, survival or reproduction of an organism, or the surrounding environment.
Examples can include
- Predators
- Competition
- Diseases
- Food availability

Question 3

What are abiotic factors? Give examples.

Answer 3

Any living factor that affects the growth, survival or reproduction of an organism, or the surrounding environment.
Climate-related factors
Light availability
Temperature
Weather
Topography
Shelter availability
Chemical factors
pH
Salinity
Dissolved gases
Trace elements.

Question 4

How does light availability affect plants and animals? Provide an example.

Answer 4

Plants: A key component in photosynthesis, affects root growth, promotes leaf expansion, determines pigment systems.
Animals: Light affects the growth, behaviour, reproduction, migration, circadian rhythm and metabolism of organisms.

The loggerhead sea turtle’s nesting processes are affected by light availability. Excess light can disorient hatchings and even deter female loggerheads from reproducing.

Question 5

How does temperature affect plants and animals? Provide an example.

Answer 5

Dormancy: The state in which an organism’s growth and activity temporarily slow/stop in an attempt to conserve energy when unfavourable conditions are present.

The arctic ground squirrel cannot tolerate below freezing temperatures in the arctic tundra. As a result, it enters a state of hibernation during winter season where its body temperature drops to sub-zero.

Question 6

How does pH affect plants and animals? Provide an example.

Answer 6

Affects enzyme activity, affects most chemical and biological processes in water.

The human stomach is a naturally highly acidic environment. This is because low pH is needed to break down and digest food, as well as kill parasites. The bacteria Helicobacter Pyloris is able to withstand the low pH of the stomach, penetrate the stomach lining and create ulcers.

Question 7

How does salinity affect plants and animals?

Answer 7

Determines the kinds of organisms found in aquatic environments
→ Saltwater vs freshwater environments (+ estuarine environments).

Question 8

What is tolerance range and how does it affect the distribution of organisms?

Answer 8

• Range of conditions a particular species can tolerate.
• Experiencing conditions outside this range results in stress.
• Wider tolerance range = more distributed throughout an environment

Question 9

Outline examples of how humans have impacted ecosystems. Describe how the 3 key spheres of Earth are affected.

Answer 9

Atmosphere: growing urban development contributes to air pollution which results in global warming, depletion of ozone layer and reduced sunlight penetration.
Lithosphere: gradual pollution and alteration of the land increases water run-off, salinity and erosion.
Hydrosphere: changes in water pH, reduced dissolved gases, rising sea levels, pollution with toxic chemicals and litter.

Question 10

What are the ways population can be distributed?

Answer 10

• Random
• Uniform
• Clumped

Question 11

What are the three factors that affect population distribution?

Answer 11

• Physical environment
  Tolerance ranges will vary from species to species. The availability of resources and suitable habitats both influence where populations can establish and sustain themselves
  • Characteristics of species
    Inherent characteristics affect where a species may choose to locate themselves. These can include levels of adaptability (i.e, if a species can adapt easily to selection pressures, then it may be more randomly distributed throughout an environment), reproductive strategies and survival tactics.
  • Behaviour of organisms
    Including migratory patterns, feeding habits, social structures.

Question 12

What are 4 processes affecting population growth?

Answer 12

• Births or germination (natality)
• Death (mortality)
• Emigration (leaving population)
• Immigration (entering population)

Question 13

Identify the types of ecosystems found in Australia.

Answer 13

1. Deserts
2. Grassland
3. Shrubland
4. Woodland
5. Temperate forests
6. Rainforests

Question 14

Differentiate between a selective pressure and a selective agent.

Answer 14

A selective agent is the organism or environmental condition that exerts a selection pressure.

Question 15

Define what a selective advantage is.

Answer 15

An increased relative ability to survive or reproduce under a given selection pressure.