B2.8 Speciation Flashcards

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1
Q

What are fossils?

A

The ‘remains’ of organisms from many years ago, and are found in rocks

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2
Q

What are the 4 ways fossils can be formed?

A
  • From the hard parts of animals that do not decay easily
  • From parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
  • When parts of the organism are replaced by other materials as they decay
  • As preserved traces of organisms - eg footprints, burrows
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3
Q

Why can scientists not be certain about how life began on earth?

A

LACK OF VALID EVIDENCE because….

  • many life forms were soft bodied which means they have left few traces behind
  • What traces there were have been mainly destroyed by geological activity
  • Fossil record is incomplete- lots of fossils not found yet
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4
Q

What can we learn from fossils?

A

how much or how little organisms have changed as life developed on Earth.

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5
Q

Give 6 reasons why extinction may be caused

A
  • changes to the environment over geological time
  • new predators
  • new diseases
  • new, more successful competitors
  • a single catastrophic event
  • through the cyclical nature of speciation
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6
Q

What is a definition for speciation?

A

The development of a new species

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7
Q

What is a species?

A

a group of similar organisms that can reproduce to give fertile offspring

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8
Q

Describe the process of speciation

A
  • 2 populations of a species become separated and isolated by a geographical barrier such as a flood or mountain range
  • There is genetic variation within the 2 populations. Each population has a wide range of alleles that control the characteristics
  • Natural selection occurs- Environmental Conditions on either side of the barrier will be slightly different. In each population, individuals with characteristics that make them better adapted to their environment have a better chance of survival and so are more likely to breed successfully. Beneficial characteristics are passed on.
  • Populations become so different that interbreeding is no longer possible
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9
Q

What does evidence from early life forms come from?

A

fossils

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10
Q

How do fossils provide evidence tat species alive today evolved from simpler life forms?

A

fossils are the remains of organisms that lived a long time ago

they show how organisms have changed over time

fossils have similar features to present-day species

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