Chapter 16 and 17: Evolution Darwin s Voyage of Discovery

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1 Chapter 16 and 17: Evolution Darwin s Voyage of Discovery Father of Evolution:. Born in England (2/12/1809) In 1831, Darwin became a naturalist on the HMS Studied and life on a mapping expedition to South America and the South Pacific. Darwin s five year trip on the Beagle led him to develop a scientific theory of biological explains how modern organisms have Observations Darwin filled his notebooks with observations throughout his voyage Noticed 3 patterns to diversity: o Species vary o Species vary o Species vary Species Vary Globally Darwin visited a wide range of habitats and noticed different, yet ecologically similar, animal species lived in separate, but ecologically similar, habitats around the globe. Examples: Australia (Emu), Africa (Ostrich), S. America (Rheas) Species Vary Locally Darwin also recognized that, yet, animal species often occupied habitats within a local area. Ex. Galàpagos Tortoises Species Vary Over Time Darwin also collected during his voyage. Noticed that some fossils of extinct animals were similar to existing species. Putting the Puzzle Pieces Together Darwin continued to study and research his observations and other individual s work. After years of research, evidence led Darwin to think that species are and that they could change by processes. Idea s that Shaped Darwin s Thinking. James Hutton and Charles Lyell: Geologists Recognized that Earth is many of years old, and the processes that changed Earth in the past are the same processes that operate in the present. o Ex:,, erosion, continental drift, etc. Jean-Baptiste Lamarck: French naturalist Published hypothesis of Inheritance of Acquired Characteristics same year Darwin was born Proposed that by selective or of organs, organisms acquired or lost certain traits during their lifetime. Traits could then be on to offspring o Over time would lead to in species

2 What did Darwin get from Lamarck? Lamarck was the first naturalist to say that species were fixed. He tried to explain evolution via processes. Recognized how the plays a role in evolution. Darwin (and others) took all of these concepts and used them when developing new ideas. Thomas Malthus English economist that said that more people were being born than were dying. Reasoned that if the human population grew unchecked, there wouldn t be enough living and for everyone. o, famine, and keep population growth in check. How did this help Darwin? Darwin thought Malthus s views applied even more to other organisms than it did to humans. Maples produce thousands of seeds each year; oysters release millions of eggs each year so why didn t they overrun the world!? Darwin realized most organisms survive and reproduce. He wondered which individuals survive and why? Artificial Selection helps to answer questions Darwin studied plant and animal breeders. He noticed that some trees produce bigger fruit than others; or some cows produce more milk than others. The breeders said that these variations can be from parents to offspring and used to livestock and crops. In artificial selection, provided the variation, but for the characteristics that they find useful. Darwin didn t know anything about genetics, but he did recognize that was present. Bred for different traits New Ideas Darwin worked out the main points of his theory of Natural Selection. Shared ideas with friends but reluctant to publish -- understood his ideas scientific and religious beliefs of his day Twenty years after writing his draft, he read an essay written by a naturalist named. Wallace s ideas were very similar to Darwin s. After more than 25 years -- published On the Origin of Species in 1859 Evolution by Natural Selection Struggle for Existence If more individuals are produced than can survive, members of a population must compete to obtain, living, and other.

3 Variation and Adaptation Individuals have natural variations that can be Some of these variations are better suited to life in an than others. An inherited characteristic that an organism s ability to and in its environment is called an. Adaptations can involve: Body parts or structures ( ) Color ( ) Physiological functions ( ) Behaviors ( ) Survival of the Fittest Darwin knew there was a between the organism s way of life and the environment that they live in. Differences in adaptation affect an individual s fitness. Fitness describes how an organism can survive and reproduce in its environment. Individuals with adaptations that are for their environment, can survive and reproduce ( fitness). Individuals that are well suited for their environment, won t survive or will have very few offspring ( fitness). Evolutionary definition of survival being able to survive in environment pass on your genes! Think about it Lions typically live in small groups called prides. The females in the pride are related (sisters, aunts, cousins, mothers). There a few young males as well. The females do most of the hunting. The dominant male lion will reproduce with the females around the same time. This makes it easier for all females to help raise the young cubs. When a new male lion fights to take over the pride, the first thing he does is kill all of the cubs why? Mechanism for Evolution Natural Selection Organisms with variations most suited to their environment survive and leave more offspring o selects for the most fit (not farmers/breeders like in artificial selection) Occurs when: o More individuals are born than can survive (struggle for existence) o Natural heritable (variation and adaptation) o Variable (survival of the fittest) Natural selection does make an organism organisms to survive and pass on their genes. If an environment changes, then adaptations that once made them more fit, may not continue to do so. o Ex: Peppered Moths

4 Common Descent Natural selection depends on an individual organism s ability to and If an organism reproduces, it leaves descendants (with each generation). Entire (well-adapted) species, then survive. Over time, successful adaptations can cause (formation of new species) Darwin proposed that all species, living and extinct, are descended from ancient common ancestors. Evidence of Evolution Darwin s four major evidences for evolution: o Biogeography o Fossil Record o Comparative Anatomy o Embryological Development Evidence at the level (after Darwin s time) Biogeography Darwin studied where organism s and the environment in which they lived. Similar species/different adaptations/different environments o Galapagos Tortoises Different species/similar adaptations/similar environments. o Many different organisms may have similar adaptations that allow them to survive the life on the Savannah The Fossil Record Fossils and radioactive dating (after Darwin) have been able to give scientists a for evolution. Fossils show over time. o Example: Related fossils (and vestigial structures) have shown that whales used to be o land mammals. Comparative Anatomy Homologous Structures o Structures that are by a related species and have been inherited by a common ancestor. o structure, function. Vestigial Structures o Inherited from ancestors, but have lost much or all of their original function due to selection acting on the descendents. o Why doesn t the vestigial structure disappear? Presence of the structure does not play a role in the fitness of the individual (no pressures acting for or against it) o Ex: Whale/dolphin: hip bone; Humans: appendix, tailbone, and goosebumps! Embryology The same group of embryonic cells develop in the same order and in similar patterns to produce many homologous tissues and organs in vertebrates.

5 Missing Information The most troubling missing information for Darwin was. Genetic information has given some of the evidence in supporting evolution. Genetic Code ( ) Homologous o More than similar structures o Similar Shared by bacteria and multicellular organisms (ex: cytochrome c for cell resp.) genes Observing Natural Selection For the most part, evolutionary changes occur too for us to see. Peter and Rosemary o Observed on the Galápagos Islands o The beak size/shape has a direct affect on the survival of the finch. o Periodic droughts would bring about frequent changes in the finch population (those with larger beaks are more likely to survive) Genetics and Natural Selection Natural Selection acts on an organism s (it does change genotype) If an organism s phenotype makes them more fit for their environment, then those organisms will be able to survive and reproduce (therefore passing on those genes for that phenotype). If the changes in a population over time, then has occurred. (not individuals)! Natural Selection is a mechanism for evolution. Organisms can also evolve in other ways: Random mutation Lateral transfer (bacteria/conjugation ) Genetic drift Gene (During sexual ) Random Mutation o Must occur in cells to be passed on. o Ex: Lizard population that is generally all brown. Mutation causes some lizards to be red and black. Red ones are quickly eaten by predators. The black ones aren t any ideas why they are surviving (they are cold-blooded reptiles)? What happens to their population number? Genetic Drift o By, in small populations some individuals with a particular allele will leave more descendants behind which means that allele will be present in the offspring. o Two types effect Disasters/diseases that reduce population size Can change genetic diversity effect Few individuals colonize new habitat Creates new allele frequencies in new population

6 The Process of Speciation Speciation can only occur when either interbreeding or the production of fertile offspring is somehow prevented: Isolation o o o isolation isolation isolation Behavioral Isolation Occurs when two populations are capable of interbreeding but have differences in rituals or other reproductive strategies that involve behavior. o Ex. Eastern and Western Meadowlarks Habitat overlaps, but will not mate with each other because they do not respond to each others song! Geographic Isolation Two populations are separated by geographic such as rivers, mountains, or bodies of water. o Ex. Colorado River separating the Abert squirrel and the Kaibab squirrel (about 10,000 years ago). Temporal Isolation Two or more species reproduce at different o Example: Orchids: Release pollen on different days, so they cannot pollinate each other. Darwin s Finches When Darwin first visited the Galápagos, he noticed many small birds with different beaks. Darwin thought they were all different types of warblers, wrens, and blackbirds. They were finches that had experienced and adapted to environments on different islands. in action!