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These notes explain how to run the ‘Highlighting Important Stages in Evolution’ activity ... - page 7 / 11

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differences between the pairs of animals that resulted in them being considered in different groups.

16.

Now use a similar principle to find out how long has it been since the following took place. You should present your estimate as a percentage of the time since life has existed on Earth:

a.

The appearance of the earliest fish. Approximately 17%. On the interactive this is the point labelled Z at which pterapis emerges. About 83% of the time that life has existed had already passed before the simplest fish appeared on the Earth.

b.

The appearance of a hollow body cavity. Approximately 20%. On the interactive we can estimate that a true hollow body cavity appeared somewhere between the emergence of acoel and velvet worms.

c.

The emergence of the first mammal. Approximately 8%, with the emergence of megazostrodon.

FURTHER WORK

1.

Animals belong to a ‘domain’ of living things called eukaryotes. Find out the other three kingdoms that fall within this domain. What are the shared characteristics of eukaryotes? What are the other two domains of living things? The other three kingdoms in Eukaryota are plants, fungi, protists. Shared characteristics are: possess membrane-bound structures or organelles such as ribosomes and vesicles; contain their genetic material within double-membraned nucleus; presence of mitochondria, the site of aerobic respiration. The other domains are archaea and bacteria – collectively called prokaryotes.

2.

Use reference sources to find out about ‘endosymbiont theory’. Discuss with your class the significance of this idea to the tree of life for animals. This is the theory that chloroplasts and mitochondria evolved from certain types of bacteria that prokaryotic cells engulfed. These cells and the bacteria trapped inside them entered a symbiotic relationship, a close association between different types of organisms over an extended time.  More specifically, the relationship was endosymbiotic, meaning that one of the organisms (the bacteria) lived within the other (the prokaryotic cells).

Curriculum links

ENGLAND

A level

AQA

Evolution has resulted in different species of organisms. They are classified into five kingdoms.

The concept of a species. Definition of species in terms of variation and potential for breeding.

The five-kingdom classification. Recognition that kingdoms are divided into phyla, classes, orders, families, genera and species.

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