B2.8 Speciation

Question 1

What are fossils?

Answer 1

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

Question 2

What are the 4 ways fossils can be formed?

Answer 2

• 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

Question 3

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

Answer 3

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

Question 4

What can we learn from fossils?

Answer 4

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

Question 5

Give 6 reasons why extinction may be caused

Answer 5

• 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

Question 6

What is a definition for speciation?

Answer 6

The development of a new species

Question 7

What is a species?

Answer 7

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

Question 8

Describe the process of speciation

Answer 8

• 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

Question 9

What does evidence from early life forms come from?

Answer 9

fossils

Question 10

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

Answer 10

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