A process by which new types of organisms develop from other existing types of organisms
Give some examples of evolution
- Amphibians evolved from fish
- Reptiles evolved from amphibians
- Birds and mammals evolved separately from reptiles
Explain how the scientific method works
- Scientists form a hypothesis for the question
- The hypothesis is tested
- Scientists test the same hypothesis in different ways - if it is upheld for most of the test, it becomes a theory
What are the main sources of evolutionary evidence?
- The fossil record
- Modification by descent and structural similarities
- Genetic similarities
- Other (such as chemical evidence from proteins)
What is a fossil?
The preserved mineralised remains of living organisms found in rock
How are geologists able to date fossils?
They look at the chemical elements that the rocks contain. By dating the rocks, they are dating the fossils
What kind of rock are fossils found in?
Sedimentary rock (rock formed from layers of water-borne sediments)
What is the study of plant and animal fossils?
How do fossils suggest that evolution has taken place?
They bear little resemblance to organisms living today indicating that species have evolved over time
When did life begin on Earth as a single-cell bacteria?
3.6 billion years ago (according to the fossil record)
What two things can fossils suggest about the earth millions of years ago?
The climate and environment
Fish fossils founds on mountains indicate that the area was covered by water in the past
What does the fossil record show us about organisms?
- How organisms have changed and developed over time
- Scientists look for differences in the ___ of body structures:
What is the difference between extinct and extant?
Extinct - fossil species
Extant - still alive today
What is convergent evolution?
- When body structures are analogous
- Same function, different origin
- Slightly different structure
Give some examples of convergent evolution
- Wings on:
- All three wing types serve the same function but each evolved independently of each other
- Have a slightly different structure
When does convergent evolution take place?
When organisms not closely related living in different ecosystems evolve similar structures or features
What is divergent evolution?
- When body structures are shared by related species
- Involves homologous structures
- These body structures were inherited from a common ancestor
- This is called modification by descent
Name some examples of divergent evolution
- Bones in the forelimbs of a _____ are similar:
- All have:
- Indicates a common ancestor
What can result from divergent evolution?
- Vestigial Structures
- Small and poorly-developed
- no useful function today
- inherited from an ancestor
Give TWO examples of vestigial structures
- Whales and some snakes that have pelvises and undeveloped hind leg bones though they have no hind limbs
- The human appendix
What can modification of body plans refer to?
Either divergent or convergent evolution
How is the embryo evidence for evolution?
- Similarities can be seen in the embryos
During early embryonic stages of development, what do all vertebrate embryos have?
- A nerve cord which becomes a spinal cord
- A supporting rod (notochord) which becomes a vertebral column
- Gill slits
- Fish-like heart
- Fish-like kidney
During the early stages of development of certain vertebrate embryos, which animals can one not tell the difference between?
- A fish
- A frog
- A chick
- A pig
- A human
What can divergent evolution also be known as?
Modification by descent
What does DNA code for?
The formation of protein molecules
What does DNA make up?
The genes that parents pass on to their offspring
How can we use DNA to show evolutionary relationships between different groups of organisms
By comparing similarities and differences between the DNA
Studies on _____ show show similaries in cell chemistry in a wide range of organisms
Cell proteins and nucleic acids
What indicates that DNA was inherited from common ancestors?
Close similarities in the DNA of different species