5-1-4 Evidence for Evolution Flashcards
Scientists almost universally accept Darwin’s theory of evolution, as it is the best available explanation for diversity on earth. What points do they agree with?
- Earth is about 4.5 billion years old
- Organisms have inhabited Earth for most of its history
- All organisms living today share common ancestry with earlier life forms.
Why are fossils important in the study of evolution?
Fossils are preserved or mineralized remains of organisms that lived long ago. They are the most direct evidence that evolution takes place. They show changes in some ancient species and the extinction of many others.
Fossils are at least how old?
They are by definition at least 10,000 years old
Some examples of fossils that indicate that evolution takes place.
Eusthenopteron - an amphibious fish
Seymouria: a reptile-like amphibian
Therapsids: mammal-like reptiles
Archaeopteryx: reveal a link between dinosaurs and birds.
What features do birds and dinosaurs have in common, indicating that birds evolved from certain type of dinosaurs?
The common features are feathers, hollow bones, and a peculiar structure to the ankle joint.
Fossil records allow us to trace the history of modern-day horse (Equus). What are the characteristics that changed over time?
The earliest known ancestor, Hyracotherium, was the size of a dog and had low-crowned molars, 4 toes on each front foot, and 3 toes on each hind foot. When grasslands replaced forest, there was a transition to durable grinding teeth and speed, with an increase in size and decrease in number of toes.
What is “The Modern Synthesis” of evolutionary theory?
It is the merge of Darwinism with Paleontology and Genetics to explain how species originate and how traits are passed on from one generation to another. Ernst Mayr did most of this work in the 1940s.
(Paleontology is a field of science that learns about early life forms by studying fossils.)
Define “population”
A group of potentially interbreeding individuals or organisms living in the same geographic area and sharing a common gene pool.
What is a “gene pool”?
The sum of all genetic information carried by members of the population.
In order for natural selection to happen, members of a population must _____ from one another.
vary. Without variation, natural selection would have nothing to act on.
How does variation among members of a population come about?
Variation arises from DNA mutations to produce new alleles.
Mutation rate (the rate of mutation): does it vary among species?
Yes, it varies among species and even among genes of an individual
What causes a large-scale mutation to happen?
When mutation is combined with other factors that reshuffle the gene pool.
