B5.2 Natural Selection And Evolution

Question 1

What is evolution?

Answer 1

• Evolution is the gradual change in a species over time

Question 2

How do organisms evolve?

Answer 2

• Organisms evolve through the process of natural selection. In a species there is normally wide genetic variation. When further mutations occur, genetic variation increases.
• This genetic variation results in a range of phenotypes. Those organisms that are best suited to their environment will survive and reproduce, passing on these advantageous characteristics through their genes. This is known as survival of the fittest.

Question 3

What are fossils?

Answer 3

• Fossils are formed when animal and plant remains, or traces, are preserved in rocks.
• The fossils found within the different rock layers are different, with the most recent layer usually found on top. The fossils layers form a sequence showing that organisms have gradually changed over time.

Question 4

What does the fossil record show? (Three points)

Answer 4

• Fossils of the simplest organisms, such as bacteria, are found in the oldest rocks, whereas fossils of more complex organisms, such as vertebrae’s, are found in more recent rocks. This supports the theory that simple life forms gradually evolved into more complex ones.
• Plant fossils appear before animal fossils. This is consistent with the fact that animals require plants to survive.
• Closely related organisms have evolved from the same ancestor. By studying similarities in anatomy, such as bone structure, scientists can show how modern day species are related to species that are now extinct.

Question 5

Other evidence for evolution - Rapid changes in a species

Answer 5

• As bacteria replicate rapidly, scientists can study evolution in action. They can observe how an advantageous characteristic, such as antibiotic resistance, becomes common in a bacterial population.

Question 6

Other evidence for evolution - Extinction

Answer 6

• Species that do not adapt to environmental changes die out.

Question 7

Other evidence for evolution - Molecuar comparison

Answer 7

• In recent years scientists have started comparing the DNA and proteins on different species. They look at the order of nuclei acid bases, or at the order of amino acids in a protein. Closely related species have the most similar DNA and proteins: those which are distantly related have fewer similarities.

Question 8

What is classification?

Answer 8

• Classification is the process of sorting living organisms into groups. The organisms within each group share similar features.

Question 9

What is one of the systems scientists use to classify organisms.

Answer 9

• One system classifies organisms at seven taxonomic levels.
• King Prawn Curry Or Fat Greasy Sausages - Kingdom, Phylum, Class, Order, Family, Genus, Species.

Question 10

What is artificial classification?

Answer 10

• Groups organisms together using observable characteristics.
• This type of classifying organisms is done by organisms having features which have the same function, not the same evolutionary origin.

Question 11

What is natural classification?

Answer 11

• Based upon the evolutionary relationships.
• Classifies species using shared features of organisms which they have inherited from their ancestors.
• Arranges the groups into a hierarchy

Question 12

Explain what phylogeny is

Answer 12

Phylogeny is the study of evolutionary links. Phylogenic links are established by studying similarities in DNA between species. The more similar the DNA, the more closely related the species are.