15 Darwin's Theory of Natural Selection. Publication of The Origin of Species

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1 Publication of The Origin of Species -He continued observing the specimens he collected and thinking about natural selection, but kept it to himself for the next 20 YEARS! -In 1858, he received a manuscript from Alfred Russell Wallace where Wallace described HIS OWN theory of evolution by natural selection! -Like Darwin, Wallace was an British naturalist and contemperary of Darwin. -He discovered natural selection observing the same kind of evidence as Darwin on ISLANDS in Malaysia. -In the cartoon, Darwin is reading Wallace s manuscript and freaking out because Wallace came up with the same hypothesis! -Darwin published The Origin of Species the next year. -Wallace didn t have such a huge amount of evidence or write as much. And Darwin was really first! -Darwin wrote about how species change over time to give rise to new species through natural selection, and supported it with much of the evidence he collected on the voyage of the beagle. 9

2 Darwin wrote about Artificial Selection -The diagram shows how all these domestic crop species were developed through artificial selection (selective breeding) from one ancestral species. -Artificial selection (selective breeding) is breeding of plants and animals to produce desirable traits. -Darwin was an avid pigeon breeder, so he Brussels Sprouts knew VERY well how artificial selection worked. -Domestication is the manipulation of species through artificial selection to serve a human purpose. Examples are most pet/working species, and plants & animals raised as food. -It supports the functional capabilities of natural selection because it works exactly like natural selection, except for what does the selecting. Cauliflower Broccoli Ancestral Species (Brassica oleracea) Kohlrabi Kale 10

3 Darwin wrote about Evolution by Natural Selection -Natural Selection (4) 1) Genetic Variation 2) Over production of offspring 3) Struggle for existence 4) Differential survival and reproduction -The Beaver cartoon represents the misconception that evolution is goal oriented. Evolution is not trying to produce perfect organisms (No such thing!). -The Gerald cartoon represents the misconception that individuals can evolve. Only populations and species evolve from one generation to the next. -The baseball cartoon represents the misconception, again, that evolution is goal oriented. Evolution was not trying to evolve land-dwelling vertebrates (tetrapods). 11

4 Darwin wrote about Inherited Variation -Before Darwin, differences between individuals of the same species were considered minor defects. -Darwin viewed them as the variation necessary for natural selection to function and species to evolve. -Variations in phenotype are due to variation in genotype (genes). -Genetic variation results from (3): 1) Gene and chromosomal mutations - Accidental mistakes during DNA replication and cell division (respectively). 2) Shuffling (recombination) of genes between parents during sexual reproduction. 3) Horizontal transfer and recombination of genes between primarily microbial individuals. -Darwin had no knowledge of this, but he did know that variable traits were passed from parents to offspring. 12 -VARIATION IS THE RAW MATERIAL OF NATURAL SELECTION!!!

5 Darwin wrote about Overproduction Of Offspring -Like variation, overproduction of offspring a crucial component of natural selection. Species tend to produce more offspring than can possibly survive. Those that do are selected for. Those that don t are selected against. -Darwin got this idea from the economist, Thomas Malthus. 13

6 -Overproduction of offspring is a problem when resources are limited (Malthus). -This leads to competition between individuals for the limiting factor. -Individuals may be forced to compete with (3): 1) Other individuals of their own population (even siblings). 2) Individuals of other populations. 3) Individuals of other species. Darwin wrote about The Struggle for Existence 14

7 Darwin wrote about Differential Survival & Reproduction -The individuals that survive are the ones with the highest fitness. -Evolutionary fitness refers to the relative ability for individuals of a population or species to survive and reproduce. -Evolutionary adaptation is a change or the process of change by which an organism or species becomes better suited to its environment (a better fit ). -Individual moths of this species are most fit due to adaptations in their behavior, morphology (straw-like proboscis with spines, barbs and hooks), and metabolism (to eat tears). 15 -The cartoon represents that stupid birds are less fit!

8 Darwin wrote about Descent With Modification -Descent with modification is the term Darwin used instead of evolution. -Lamarck s hypothesis was inheritance of acquired characteristics (wrong!). -Giraffe populations had variation in neck length. Individuals with longer necks were better able to feed, and therefore survive and reproduce (more fit). These individuals were selected for, and pass their long-neck genes to their offspring. Those with shorter necks (less fit) were selected against. -The units that change are populations and/or species. -Desirable traits (adaptations) increase in the population. 16