B2.8 Speciation Flashcards
What are fossils?
The ‘remains’ of organisms from many years ago, and are found in rocks
What are the 4 ways fossils can be formed?
- 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
Why can scientists not be certain about how life began on earth?
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
What can we learn from fossils?
how much or how little organisms have changed as life developed on Earth.
Give 6 reasons why extinction may be caused
- 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
What is a definition for speciation?
The development of a new species
What is a species?
a group of similar organisms that can reproduce to give fertile offspring
Describe the process of speciation
- 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
What does evidence from early life forms come from?
fossils
How do fossils provide evidence tat species alive today evolved from simpler life forms?
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