Resource Description

Effects of the Environment on Organisms 

Inquiry Question 1:How do environmental pressures promote a change in species diversity and abundance?

• Predict the effects of selection pressures in ecosystems, including:
  • Biotic factors – living (fungi, plants)
  • Abiotic factors- non living ( wind)

Biotic Factors

Biotic selection pressures that affect ecosystems:
– Availability of food → low food availability = decreases in population + abundance
– Mates → able to find mate = reproduction + increase in population + abundance
– Predators → high amount of predators = decrease in prey population + abundance
– Competitors → high amount of competitors = competition for resources + decrease in population 

If biotic selection pressures are positive  → population abundance and diversity increase. If selection pressures are negative → population abundance and diversity decrease.

Abiotic factors

Abiotic selection pressures that affect ecosystems:
– temperature
– oxygen availability → low oxygen = low respiration + decrease in organisms that can inhabit the environment
– water availability → low water = competition for water + decrease in abundance species 

If abiotic selection pressures are positive → increase in abundance and diversity. If abiotic selection pressures are negative → decrease in abundance and diversity 

• Investigate changes in a population of organisms due to selection pressures over time, for example:
  • Cane toads in Australia
  • Prickly pear distribution in Australia 

Cane toads in Australia 

Introduced as biological control for cane beetle. No natural predators → +ve selection pressure, population increased. Increased food source of native fauna → +ve selection pressure. Toads became fast moving and directional due to spatial sorting → +ve selection pressure. Larger size and longer legs → +ve selection pressure. Development of arthritis in older, larger toads → -ve selection pressure. Overall population increase due to +ve selection pressures.

Prickly pear distribution in Australia 

The prickly pear was introduced to use the insects that feed on it. It was moved around Australia by people as food source for livestock. Good in arid climates → positive selection pressure, ↑ in population. Methods for removal were not effective + population ↑ rapidly. Cactoblastis moth introduced as biological control. Placed moths on the pear → larvae eat through cactus pad → plant dies. After 7yrs population was removed. 

+ve selection pressure → Aust. climate
-ve selection pressure → moth

Adaptations 

Inquiry Question 2: How do adaptations increase the organism’s ability to survive?

• Conduct practical investigations, individually or in teams, or use secondary sources to examine the adaptations of organisms that increase their ability to survive in their environment, including:
• • Structural adaptations

are anatomical features that improve an organism’s ability to cope with abiotic and biotic factors in their enviro. Appropriate adaptations increase the chance of survival and reproduction. Body shape and size are structural adaptions. Example: thick fur to survive the cold

• • Physiological adaptations

internal features of an organisms that enable them to survive in their enviro. Example: camouflaging.

• • Behavioural adaptations 

are actions that an organism takes to improve survival and reproduction. Example: seeking or leaving shade/ shelter.

• Investigate, through secondary sources, the observations and collection of data that were obtained by Charles Darwin to support the Theory of Evolution by Natural Selection, for example:

Charles was an English naturalist who sailed on HMS BEGAN. He collected specimens from every location the ship visited. In 1858 Charles proposed a process by which evolution occurs called “natural selection”

• • Finches of the Galapagos Islands 

he visited the Galapagos island in 1835. During his visit he realised finches were similar on diff islands and showed distinct variation in beak size and structure. He realised beaks