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BIOLOGY, M4 EQ-Bank 10

Ecosystems are dynamic, shaped not only by physical forces but also by the living organisms within them. Including a specific example, explain one biotic factor that has significantly impacted past ecosystems:

  1. Over a relatively short timescale (within a few decades or centuries)   (2 marks)
  2. Over an extended geological timescale (millions of years)   (2 marks)
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a.   Short timescale biotic factor: introduction of invasive species

  • The introduction of cane toads in Australia in 1935 has rapidly altered local ecosystems within decades.
  • Cane toads have caused declines in native predator populations that attempt to eat the toxic toads, leading to cascading effects throughout the food web. 

b.   Geological timescale biotic factor: evolution of land plants

  • The development of land plants around 470 Mya led to increased oxygen production, soil formation, and the creation of new habitats.
  • This gradual but profound change altered atmospheric composition and weather patterns. This reshaped terrestrial ecosystems and paved the way for the evolution of terrestrial animal life.
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a.   Short timescale biotic factor: introduction of invasive species

  • The introduction of cane toads in Australia in 1935 has rapidly altered local ecosystems within decades.
  • Cane toads have caused declines in native predator populations that attempt to eat the toxic toads, leading to cascading effects throughout the food web. 

b.   Geological timescale biotic factor: evolution of land plants

  • The development of land plants around 470 Mya led to increased oxygen production, soil formation, and the creation of new habitats.
  • This gradual but profound change altered atmospheric composition and weather patterns. This reshaped terrestrial ecosystems and paved the way for the evolution of terrestrial animal life.

BIOLOGY, M4 EQ-Bank 9

Over geological timescales, our planet's ecosystems have undergone dramatic transformations. Name and briefly explain two abiotic factors that have played significant roles in driving these long-term changes in past ecosystems.   (2 marks)

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  • Two significant abiotic factors that have contributed to changes in past ecosystems over long periods of time are climate change and plate tectonics.
  • Long-term climate changes, such as ice ages and warming periods, have dramatically altered global temperatures and precipitation patterns, leading to shifts in vegetation types and animal distributions.
  • Plate tectonics, including continental drift and mountain formation, have reshaped landscapes over millions of years. It has created new oceans and influenced global climate patterns, all of which have had profound effects on the evolution and distribution of species.
Show Worked Solution
  • Two significant abiotic factors that have contributed to changes in past ecosystems over long periods of time are climate change and plate tectonics.
  • Long-term climate changes, such as ice ages and warming periods, have dramatically altered global temperatures and precipitation patterns, leading to shifts in vegetation types and animal distributions.
  • Plate tectonics, including continental drift and mountain formation, have reshaped landscapes over millions of years. It has created new oceans and influenced global climate patterns, all of which have had profound effects on the evolution and distribution of species.

BIOLOGY, M4 EQ-Bank 8

Explain how the unique abiotic factors of the Australian continent have influenced the evolution of sclerophyll plants. In your answer, provide two specific adaptations.   (4 marks)

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  • The evolution of sclerophyll plants in Australia is closely tied to the continent’s abiotic factors, particularly its nutrient-poor soils, arid climate, and frequent bushfires.
  • These plants have developed tough, leathery leaves with a thick cuticle to reduce water loss in the dry Australian environment, a key adaptation to water scarcity.
  • Sclerophyll species like eucalypts and banksias have also evolved strategies to cope with nutrient-poor soils, such as cluster roots that efficiently extract phosphorus.
  • Many sclerophyll plants have developed fire-resistant adaptations, including lignotubers for post-fire regeneration and fruits that release seeds after fire.
  • These adaptations demonstrate how the challenging abiotic conditions in Australia have acted as strong selective pressures, shaping the evolution of a unique flora highly specialised for survival in this harsh environment.
Show Worked Solution
  • The evolution of sclerophyll plants in Australia is closely tied to the continent’s abiotic factors, particularly its nutrient-poor soils, arid climate, and frequent bushfires.
  • These plants have developed tough, leathery leaves with a thick cuticle to reduce water loss in the dry Australian environment, a key adaptation to water scarcity.
  • Sclerophyll species like eucalypts and banksias have also evolved strategies to cope with nutrient-poor soils, such as cluster roots that efficiently extract phosphorus.
  • Many sclerophyll plants have developed fire-resistant adaptations, including lignotubers for post-fire regeneration and fruits that release seeds after fire.
  • These adaptations demonstrate how the challenging abiotic conditions in Australia have acted as strong selective pressures, shaping the evolution of a unique flora highly specialised for survival in this harsh environment.