Year 10 Science · Unit 1 · Lesson 15

Speciation and Reproductive Isolation

Foundation Worksheet

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Date

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Learning Goals

Define species, reproductive isolation and allopatric speciation.
Describe the steps by which a physical barrier leads to the formation of a new species.
Give Australian examples of speciation driven by geographic isolation.

Warm Up

Order the steps

Number the events from 1 to 7 to show the correct order of allopatric speciation. Event 1 = what happens first.

Order	Event
	Genetic differences have accumulated to the point where the two populations can no longer interbreed, a new species has formed.
	A single population of a species lives in one area with gene flow between all individuals.
	The two separated populations face different selection pressures and begin to evolve in different directions.
	A physical barrier, such as a mountain range, ocean or river, divides the population into two isolated groups.
	Gene flow between the two populations stops completely because the barrier prevents individuals from meeting.
	Genetic differences between the two populations continue to accumulate over many generations.
	Reproductive isolation is established, even if the barrier disappeared, the two groups would not successfully interbreed.

Your Turn

Fill the gap

Choose the correct word from the word bank to complete each sentence.

allopatric speciation reproductive isolation gene flow natural selection geographic barrier sympatric speciation fertile offspring marsupials

A species is defined as a group of organisms that can interbreed and produce . When a such as a mountain range or ocean, divides a population, between the two groups stops. This process, where two new species arise from geographically separated populations, is called . Over time, acts differently on each population because they face different environments. Eventually, is established, the two groups cannot interbreed even if the barrier disappears. In contrast, occurs within the same geographical area, though this is less common. Australia's unique diversified through 50 million years of isolation from other continents.

Show What You Know

1. What is the biological species concept? Give one example of two organisms that meet this definition.

Recall 2 marks

2. What is the difference between allopatric and sympatric speciation? Which is more common and why?

Recall 2 marks

Wrap Up

In one sentence, what was the main idea of this lesson?