Evolution What Darwin Never Knew

Evolution Change over time Modern organisms have descended from ancient organisms.

Evolution Myths Man evolved from monkeys. Evolution does not state that man evolved from monkeys. It states that we shared a common ancestor. Darwin came up with the theory of evolution. The theory existed before Darwin Evolution is JUST a theory: A well supported, testable explanation of phenomena that have occurred in the natural world.

Charles Darwin Born: 1809 in England Religious Beliefs: Darwin was a Christian for a majority of his life and later became an agnostic.

Voyage of the Beagle Darwin set sail for 5 years on the H.M.S. Beagle in 1831 While on the Beagle, Darwin made several observations and inferences that lead him to develop his theory of evolution.

Patterns of Diversity  Darwin was surprised at: how many plants and animals seemed well-suited for their environments. how different organisms were in similar ecosystems of different continents.

Charles Darwin Born in England – 1809 Sailed on the HMS Beagle’s five-year voyage mapping the coastline of South America. Observed and recorded characteristics of species on the trip Developed a scientific theory of biological evolution - explains how modern organisms evolved over long periods of time through descent from common ancestors. Wrote On the Origin of Species Darwin's Finches

Darwin’s 3 patterns of biodiversity Species vary globally Species vary locally different, yet related, animal species often occupied different habitats within a local area Species vary over time

Species vary globally Different, yet ecologically similar, animal species inhabited separated, but ecologically similar, habitats around the globe found flightless, ground-dwelling birds that were similar on different continents. South America = rheas Africa = ostriches Australia = emu.

Species vary locally Different, yet related, animal species often occupied different habitats within a local area Galapagos Islands – the shape of the tortoises’ shells corresponds to different habitats. Isabela Island has high peaks, is rainy, and has abundant vegetation that is close to the ground. A tortoise from Isabela Island has a dome- shaped shell and short neck. Hood Island, in contrast, is flat, dry, and has sparse vegetation. A long neck and a shell that is curved and open around the neck and legs allow the Hood Island tortoise to reach sparse, high vegetation.

Species vary over time Darwin collected fossils = the preserved remains or traces of ancient organisms. Darwin noticed that some fossils of extinct animals were similar to living species. He discovered fossils of Glyptodont where armadillos currently live. Why did Glyptodont disappear Why did they resemble armadillos?

Scientists who shaped Darwin’s thinking Hutton and Lyell - geologists The earth is extremely old Processes that changed the past are the same that operate in the present

Scientists who shaped Darwin’s thinking etc. Lamarck – Although his ideas were FLAWED they shaped Darwin’s thinking Organisms could change during their lifetimes by selectively using or not using various parts of their bodies Individuals could pass these acquired traits on to their offspring, enabling species to change over time. Organisms have an inborn urge to become more complex and perfect, and to change and acquire features that help them live more successfully in their environments.

Scientists who shaped Darwin’s thinking etc. Malthus = if the human population grew unchecked, there wouldn’t be enough living space and food for everyone War, famine and disease would work against population growth Darwin realized that most organisms don’t survive and reproduce, he wondered which individuals survive…and why?

Artificial selection Artificial selection = process in which nature provides the variations, and humans select those they find useful. Darwin put artificial selection to the test by raising and breeding plants and fancy pigeon varieties.

16.3 Natural selection Natural selection = the process by which organisms with variations most suited to their environment survive and leave more offspring Natural selection occurs when there is 1) A struggle for existence – more offspring are produced than can survive 2) Variation and adaptation 3) Survival of the fittest

1) Struggle for existence Grasshoppers can lay more than 200 eggs at a time, but only a small fraction of these offspring survive to reproduce.

2) Variation and Adaptation Adaptation = heritable characteristic that increases an organism’s ability to survive and reproduce in its environment EX. Green color is an adaptation: The green grasshoppers blend into their environment and so are less visible to predators.

3) Survival of the Fittest Fitness = the ability of an organism to survive and reproduce Because their color serves as a camouflage adaptation, green grasshoppers have higher fitness and so survive and reproduce more often than yellow grasshoppers do.

Natural Selection Green grasshoppers become more common than yellow grasshoppers in this population over time. More grasshoppers are born than can survive Individuals vary in color and color is a heritable trait Green grasshoppers have higher fitness in this particular environment

Natural Selection Natural selection does not make organisms “better”. It is a process that enables organisms to survive and reproduce in a local environment. If local environmental conditions change, some traits that were once adaptive may no longer be useful Salamander Evolution

Principle of common descent According to the principle of common descent, all species—living and extinct—are descended from ancient common ancestors. Darwin proposed that, over many generations, adaptation could cause species to evolve into new species. He also proposed that living species are descended, with modification, from common ancestors—an idea called descent with modification.

Evidence for Evolution Age of the Earth and Fossils Radioactive dating of rocks indicate that Earth is about 4.5 billion years old—plenty of time for evolution by natural selection to take place. Since Darwin, paleontologists have discovered hundreds of fossils that document intermediate stages in the evolution of many different groups of modern species

Evidence for Evolution Homologous Structures Homologous Structures – structures that are shared by related species and are inherited from a common ancestor For example, the front limbs of amphibians, reptiles, birds, and mammals contain the same basic bones.

Evidence for Evolution Vestigial structures are inherited from ancestors, but have lost much or all of their original function due to different selection pressures acting on the descendant. Ex. hipbones of bottlenose dolphins In ancestors, hipbones played a role in terrestrial locomotion. As the dolphin lineage adapted to life at sea, this function was lost Why would an organism possess structures with little or no function? The presence of a vestigial structure does not affect an organism’s fitness. Natural selection would not eliminate it.

Evidence for Evolution Embryology Similar patterns of embryological development provide evidence that organisms have descended from a common ancestor. Researchers noticed a long time ago that the early developmental stages of many animals with backbones (called vertebrates) look very similar. PBS embryology clip Which Embryo?

Evidence for Evolution Genetics & Molecular Biology At the molecular level, the universal genetic code and homologous molecules provide evidence of common descent. DNA and RNA carry information from generation to generation and to direct protein synthesis Similar genes and proteins are found in many organisms Hox genes – determine the head- to-tail axis in embryonic development

Classification

Why Classify? The goal of systematics is to organize living things into groups that have biological meaning By using a scientific name, biologists can be sure that they are discussing the same organism. Ex. cougar, puma, panther, and mountain lion can all be used to indicate the same animal— Felis Concolor.

Linnaean Classification System Organizes living things into groups (taxa) that have biological meaning Linnaeus grouped species according to anatomical similarities and differences Linnaeus’s classification system includes seven hierarchical taxa: species, genus, family, order, class, phylum, and kingdom.

Classification

Binomial Nomenclature Linnaeus developed a two- word naming system in the 1730s= binomial nomenclature The scientific name is written in italics The first word begins with a capital letter The second word is lowercase EXAMPLE : Genus species Polar bear = Ursus maritimus

Dichotomous Key Used to identify organisms Consists of paired statements that describe alternative characteristics for an organism.

Problems with Traditional Classification Organisms that look alike are not always the most closely related Which two are most closely related? Dolphin wolf shark

Cladogram Cladogram = illustrates how groups of organisms are related to one another by showing how evolutionary lines, or lineages, branched off from common ancestors.

The 6 Kingdoms

The 3 Domains Genetic analysis shows the two prokaryotic kingdoms are more different from each other, and from eukaryotes Domain = a larger, more inclusive category than a kingdom.

The Tree of Life