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Chapter 16 and 17 Microevolution.

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Presentation on theme: "Chapter 16 and 17 Microevolution."— Presentation transcript:

1 Chapter 16 and 17 Microevolution

2 Evolution The change in a species over time.
The processes that have transformed life on earth from it’s earliest forms to the vast diversity that characterizes it today.

3 Early Ideas About Evolution
Many of the early ideas regarding the existence of living organisms were strongly influenced by religion and philosophy. However, in the 1600s, scholars began a revolution that created the basis of empirical and scientific thought.

4 Early Ideas About Evolution
1. Hippocrates Proposed that all things can be traced to preceding causes. 2. Aristotle Believed that each kind of organism was distinct from all the rest. Classified organisms into two groups: plants and animals 3. Georges de Buffon (1700s) proposed that species shared ancestors instead of arising separately. Suggested that Earth was much older than 6000 years

5 Proposed that all organisms evolved toward perfection and complexity.
4. Jean Baptiste Lamarck (early 1800’s) Proposed that all organisms evolved toward perfection and complexity. theory of inheritance of acquired characteristics- changes in an environment caused an organism’s behavior to change, leading to greater use or disuse of a structure or organ. For example the giraffe: short neck giraffes needed to reach leaves higher in trees, so they stretched their neck to reach them. This stretched neck was passed on to offspring, who in turn, stretched their own necks and passed on that neck to their offspring.

6 6. Georges Cuvier (early 1800s)
5. James Hutton (late 1700s) Proposed that the changes in landforms resulted from slow changes over a long period of time (Theory of Gradualism). 6. Georges Cuvier (early 1800s) proposed the Theory of Catastrophism - natural disasters have shaped landforms and caused species to become extinct. 7. Charles Lyell (1830s) Proposed the Theory of Uniformitarianism -geologic processes that shape Earth are uniform over time.

7 Struggle for Survival Thomas Malthus -proposed that resources such as food, water, and shelter were natural limits to population growth. -Human population would grow uncontrollably without limits. As a result, Darwin suggested that -A similar struggle takes place in nature. -Resources are limited, and organisms had more offspring than could survive.

8 Charles Darwin “Father of Evolution”
Influenced by Charles Lyell who published “Principles of Geology”. In 1831, Darwin, on the ship HMS Beagle, set sail from England to map the coast of South America.

9 While on the Galapagos Island, he observed the following:
Species found on one island differed from those on nearby islands. (Variation) Some differences seemed well suited to the animals’ environments and diets. Fossils provided evidence of species changing over time. Fossils suggested that modern animals might be related to fossil forms. Fossil shells of marine organisms were found high up in the Andes mountains.

10 After his voyage When he returned in 1836, Darwin began discussing his ideas with other scientists.

11 According to Darwin’s ideas, evolution occurs from generation to generation due to two interacting factors: 1) Genetic Variation Differences occur among individuals of a given species. 2)Natural Selection In each generation, many more offspring are produced than will survive. Individuals with more favorable traits will be better suited for the environment. Over time, favorable traits will become more prevalent in a population.

12 Artificial Selection Darwin noticed a lot of variation among domesticated plants and animals as a result of artificial selection. process in which humans/breeders choose as parents those individuals with traits that are desirable from a human perspective. the underlying cause of the phenotypic variation is usually related to differences in alleles that determine the trait. through the selection of certain traits, breeders can produce a great amount of diversity.

13 Main Principles of Natural Selection
Variation Differences exist in every population. Overproduction many offspring raises the chance of survival but results in competition between offspring for resources. Adaptation better adapted = better chances of survival. Descent with Modification Over time, natural selection will result in more individuals being well suited for the environment if conditions remain favorable.

14 Natural Selection can occur in several ways:
1)Directional Selection -new allele introduced into a population by mutation 2) Stabilizing Selection -reduces genetic diversity

15 3) Diversifying Selection -Likely occur in populations that occupy heterogeneous environments-so some members are more likely to survive than others. 4) Balancing Selection -maintains genetic diversity

16 Evidence of evolution

17 Evidence of Evolutionary Change
Fossil record Comparative Anatomy Embryonic development Studies of natural selection Selective breeding Molecular structure (DNA, Amino Acid sequence)


19 Fossil Records provide evidence that living things have evolved
Fossils show the history of life on earth and how different groups of organisms have changed over time

20 Comparative Anatomy scientific study of comparable body parts in order to identify similarities and differences.

21 Homologous Body Structures
Structures that have different mature forms but develop from the same embryonic tissues e.g. Wing of bat, human arm, leg of turtle Turtle Alligator Bird

22 Homologous Body Structures

23 Analogous Structures Similar features of organisms that evolve independently. Examples: Wings structure in various flying animals same function but differ in bone structure, wing coverings, shape, and sizes fins Animals such as penguins and fish both have fin-like structures

24 Vestigial Structures Bones or other structures present in organisms but are reduced in size and function. Example: Hind leg and hip bones in whales

25 Similarities in Embryology
the study of the development of an embryo from fertilization to the fetus stage. In their early stages of development, chickens, turtles and rats look similar, providing evidence that they shared a common ancestry.

26 Embryological development

27 Speciation –Development of new species
Chapter 17 Speciation –Development of new species

28 Species refers to a particular kind of organism.

29 Differences in phenotype do not disqualify some members
Ernst Mayr is used to define characteristics particular to one kind of animal. “Species are groups of interbreeding natural populations that are reproductively isolated from other such groups.” Differences in phenotype do not disqualify some members

30 Mayr’s definition does not apply to asexual creatures (as they do not have an extensive gene pool – each offspring being a clone of the parent), but it does help classify sexually reproducing organisms.

31 Extinction The irrevocable loss of one species. Example – the loss of the dodo bird

32 Mass Extinction Loss of several species at once due to a catastrophic event. The loss of dinosaurs could be considered mass extinction.

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