1CHAPTER 4
EVOLUTION AND BIODIVERSITY
Evolution - theory that concerns how organisms change over time.
-change is very slow and only in minor ways
Evidence of Evolution:
1) the fossil record - most common form of evidence
2) chemical analysis
3) DNA analysis
4) ice core drillings
Ways of Classifying Organisms:
Species - a group of similar organisms that share a common ancestor and do not reproduce outside the group.
The more closely related a species, the more similar their structures will be.
A. Homologous structures - anatomical parts with structures that are very similar, even though they have entirely different functions.
Examples - bones in a whale’s flipper
- a human’s arm
- a bat’s wing
B. Vestigial structures - anatomical structures that have degenerated and seem to serve no function.
Examples - tail-bone, wisdom teeth, appendix
- Boas and whales - small hip and leg bones
C. Analogous structures - anatomical structures that have the same function but are NOT similar in structure.
Examples - wing of a bird and wing of a butterfly
Patterns of Evolution
1. Divergent evolution - the process by which related species become less alike; evolve into a variety of species.
-leads to speciation -the formation of a new species.
Ex. - polar bears diverged from brown bears
-camels and llamas
-also results in adaptive radiation - the process by which members of a species adapt to a variety of habitats.
Ex. - Darwin’s finches - 13 different variations
-biodiversity is believed to be the result of speciation and extinction.
The movement of tectonic plates influences evolution by changing the locations of continents, causing some species to be geographically isolated from others.
Geographic isolation -when a physical barrier separates a population into groups.
-can result from - mountain ranges
- volcanic eruptions - lava flows
- rivers
- earthquakes
- deforestation
- continents
- islands
2. Convergent evolution - the process by which distantly related organisms develop similar characteristics.
-occurs when different species share the same environmental surroundings.
Ex. - whales and dolphins (mammals) now resemble fish
-can often lead to cases of mimicry - the evolution of one organism so it comes to resemble or look like another.
Ex. - Queen Anne’s butterfly closely resembles the toxic Monarch butterfly.
Over the course of time, the change in the gene pool of one species may leadto the change of the gene pool of another species. This process is called coevolution.
Ex. - bats and moths
Can individual organisms evolve? NO!!!
Biological evolution is based on changes in a population’s genetic makeup over time.
Populations evolve due to variations within, but individuals can’t develop new structures.
How does the genetic makeup change?
Through mutations
Mutation - a change in DNA
Mutations are a source of new genetic material.
They add genetic material to a gene pool thereby increasing variation within the population.
Mutations are sometimes beneficial.
Causes of mutations:
-ultraviolet light
-X-rays
-radioactivity
-certain chemicals (mutagens)
-random errors in DNA coding
Terms:
Adaptation
Genetic engineering
Selective breeding
Generalist species