Darwin and Evolution Chapter 15

HISTORY OF EVOLUTION THOUGHT 15.1

Charles Darwin In 1831, 5-year voyage on British naval vessel HMS Beagle as the ship’s naturalist. He collected and recorded geological and biological diversity he saw during the voyage.

Charles Darwin He supported the idea that species had remained unchanged since the time of creation. Evolution- proposes that genetic change occurs in a species over time, which leads to phenotypic differences.

Mid-Eighteenth Century Influences Plato- every species has a “perfect” form, species variation is just the imperfections. Taxonomy- the science of classifying organisms. Explores brought back extant (still in existence) and fossils to be compared to known living species.

George Cuvier- founded paleontology (study of fossils) – Thought species were “fixed” – But fossils didn’t match up – Maybe from local catastrophes Followers suggested giant catastrophe then God created a whole new species - catastrophism Late-Eighteenth Century Influences

Lamarck – more complex organisms are descended from less complex organisms ✓ – Striving for perfection ✗ Inheritance of acquired characteristics- environment can produce physical changes in a lifetime that are inheritable. ✗ Late-Eighteenth Century Influences

Hutton- extreme geographical changes can be explained by slow, natural processes. Uniformitarianism- natural processes witnessed today are the same processes that occurred in the past. – We now know that rates of change have not always been uniform throughout history. Late-Eighteenth Century Influences

Thomas Malthus- studied the factors that influence the growth and decline of human population. Limit the quantity of resources, species will decline. Late-Eighteenth Century Influences

Questions? 1.Who proposed catastrophism and how was it disproved? 2.Evaluate Lamarck’s idea of inheritance of acquired characteristics as an explanation of biological diversity.

DARWIN’S THEORY OF EVOLUTION 15.2

Charles Darwin Medical school at 16. Didn’t like it. Botanist friend told him to go on the HMS Beagle voyage as a naturalist. Didn’t get paid. Took 5 years.

Observation of Changes over Time Argentina had raised beaches where layers of sediment were exposed. Fossil remains of armadillo-like animal size of a small car. Fossil remains of a 3 m tall ground sloth. From this, we know species change over time. Not “fixed”

Biogeographical Observations Biogeography- study of the geographical distribution of organisms throughout the world. South African animals were different from those in Europe. Similar environments has similar looking animals.

Biogeographical Observations The Galapagos Islands are a small group of volcanic islands too far from the mainland for more animals and plants to colonize, yet life was still there. Species were slightly different from island from island. Tortoise neck length correlated with variation in vegetation.

Biogeographical Observations Darwin’s famous observation from Galapagos Islands is the finches. – Variation of beak size and shape

Natural Selection and Adaptation Darwin concluded early on that species change over time and are not fixed entities crafted by a creator.

Natural Selection: 1.Organisms exhibit heritable variation. 2.Organisms compete for available resources. 3.Individuals in a population differ in reproductive success. 4.Organisms adapt to conditions as environment changes.

Organisms Have Heritable Variation Before Darwin, variations were “imperfections”. Genetic variation arises by chance and for no real purpose. – Harmful, helpful, neutral Harmful is eliminated by natural selection Helpful and neutral can be maintained BUT helpful mutations increases reproductive success.

Organisms Compete for Resources He realized if all offspring born to a population were to survive, insufficient resources would be available to support it.

Organisms Differ in Reproductive Success Some individuals have favorable traits that enable them to better compete for resources.  get more resources  more energy toward reproduction Fitness- reproductive success of an individual relative to other members of a population. Ex: background matching

Organisms Become Adapted Adaptation- any evolved trait that helps an organism be more suited to its environment. Ex: penguins and sea turtles, Venus flytrap

We Can Observe Selection at Work Selectively breeding for certain traits. Artificial selection- intentional breeding of certain traits to produce desirable outcome. Ex: Dogs, Finches and seasons

EVIDENCE FOR EVOLUTION 15.3

Fossil Evidence Fossils- remains and traces of past life or any other direct evidence of past life. Transitional Fossils- resemblance of two groups that in the present are classified separately.

Fossil Evidence Fossils have been discovered that support the hypothesis that whales had terrestrial ancestors.

Biogeographical Evidence Geography separates continents, islands, and seas, we might expect a different mix of plants and animals.

South America, Antarctica and Australia were all originally connected. Marsupials evolved from egg-laying mammalian ancestors. – Today they are endemic to South America and Australia. Biogeographical Evidence

Anatomical Evidence Vertebrate forelimbs are used for flight, orientation during swimming, running, climbing, and swinging. Homologous- structures that are anatomically similar because they inherited from a common ancestor. Analogous- structures serve same function but originated independently.

Anatomical Evidence Vestigial structures- anatomical features that fully developed in one group but reduced and may have no function in the other. Ex: tail bone and wisdom teeth.

Biochemical Evidence ALL living organisms use the same basic biochemical molecules, including DNA, RNA, and ATP. Organisms use codons to code for proteins. Genetic code is universal in living organisms.

Criticisms of Evolution No longer a hypothesis. Some propose other mechanisms founded in religious philosophy. Misconceptions: – Evolution is a theory about how life originated. Following the origin of life. – No transitional fossils. Not everything can be preserved. – Evolution proposes that life changed as a result of random events. Not all by chance, natural selection shapes – Not observable or testable, so not science.