M3.1 Case Studies

Question 1

Impact of change in physical abiotic conditions (sea ice cover loss)

Answer 1

Loss of sea ice cover in the Antarctic is decreasing krill populations → food become scarce for Adelie penguins and leopard seals, who rely on krill as a primary food source → leopard seals may begin to prey more heavily on Adelie penguins.

Adelie penguins only lay 2 eggs/female/year and chicks are hatching faster into periods of food scarcity due to warming temperatures in the Antarctic → Adelie penguin population threatened by leopard seal predation + decreasing survival rate of chicks

Question 2

Impact of introduction of species (cane toads)

Answer 2

Introduction of cane toads severely impacted native animal populations in Australia. Cane toads are poisonous at every stage of their lives → native animals that eat them, like the northern quoll, become poisoned and die → as a result, frog-eating species e.g. goannas, quolls, king brown snakes population become threatened by the introduction of cane toads to their native environment

Question 3

Controlling pest species (prickly pear)

Answer 3

Prickly pears were introduced to Australia in 1788 on the First Fleet, to start a cochineal dye industry. However, they were able to reproduce quickly by seed + thrived in semi-arid environments (drought tolerant and succulent), reproduction sped up by fire and strong winds → population spread out of control.

Human control:
- Chemical herbicides - ineffective as it takes 2-3 years for prickly pear to die following application + herbicides could kill other plants nearby
- Physical removal - ineffective due to large area covered by PP populations + PP can regenerate quickly from a single seed or stem

Biocontrol agents:
- Cactoblastis moth - very effective. Cactoblastis moth larvae eat prickly pear, so PP and CM populations naturally fluctuate together

Question 4

Controlling pest species (rabbits)

Answer 4

Rabbits introduced in 1859 to be hunted for sports. Extremely high reproduction rate (184 young in 18 months, sexual maturity reached at 3-4 months of age)

Human control:
- Destroy warrens: effective. Impede growth of young
- Toxins: effective. Pindone and 1080 toxin kills rabbits upon ingestion

Biocontrol agents:
- Dogs: VIC government passed guidelines for killing rabbits using dogs
- Most effective: virus. Almost eradicated pest population but resistant rabbits have evolved.

Question 5

ecosystem

Answer 5

groups of organisms and the non-living environment interacting together as a complex self-sustaining natural system.

Question 6

selection pressure

Answer 6

The a/biotic factors of an environment that affect an organism’s behaviour, survival, and reproduction.

Question 7

natural selection

Answer 7

Mechanism of evolution:
relies on genetic diversity, which means that different individuals may be more adapted to particular environments or environmental changes, and therefore more likely to survive under the selection pressures presented by the environment. Those organisms that survive will reproduce and pass on their favourable trait to their offspring, increasing the number of organisms in the next generation that possess the favourable trait.

Question 8

impact of introduced species

Answer 8

Agriculture: Competition with crops/livestock
Native wildlife: competition of food, water, shelter, Predation - reducing biodiversity of native wildlife
Soils: overgrazes native plants, or weeds take over- erosion, land degradation