Evolution 15-1

Evolution “Change in a species over time” The process by which modern organisms have descended from ancient organisms

Evolution is a Theory A well supported testable explanation of phenomena that have occurred in the natural world A well supported testable explanation of phenomena that have occurred in the natural world

Charles Darwin Contributed the most to the understanding of evolution Contributed the most to the understanding of evolution Traveled for five years on the H.M.S. Beagle Traveled for five years on the H.M.S. Beagle During his trip he made numerous observations and collected evidence that led him to propose the theory of evolution During his trip he made numerous observations and collected evidence that led him to propose the theory of evolution

Patterns of Diversity Darwin noticed that different parts of the world had different species living there. Darwin noticed that different parts of the world had different species living there. Example… Argentina and Australia have very similar grasslands but the animals that live there are very different Example… Argentina and Australia have very similar grasslands but the animals that live there are very different Why are there rabbits in England and kangaroos in Australia? Why are there rabbits in England and kangaroos in Australia?

Fossils - Preserved remains of dead organisms Darwin collected a lot of Fossils Darwin collected a lot of Fossils Some of the fossils resemble organisms that were still alive, others are completely different Some of the fossils resemble organisms that were still alive, others are completely different Why did so many species die and disappear? Why did so many species die and disappear?

The Galapagos Islands Influenced Darwin the most Influenced Darwin the most Each of the island were close together but had very different climates Each of the island were close together but had very different climates The land tortoises and iguanas on the islands varied in predictable ways from one island to another. The land tortoises and iguanas on the islands varied in predictable ways from one island to another. –You could tell which island a tortoise was from based on the shape of its shell.

Finches Darwin saw several types of small brown birds hopping around looking for seeds Darwin saw several types of small brown birds hopping around looking for seeds Darwin collected some specimens and made many observations of these finches Darwin collected some specimens and made many observations of these finches He noticed that some of the birds had differently shaped beaks. He noticed that some of the birds had differently shaped beaks.

Ideas that shaped Darwin’s thinking Most of the people in Europe believed that life was created only a few thousand years before Most of the people in Europe believed that life was created only a few thousand years before Plants, animals and even geological features have been the same since their creation. Plants, animals and even geological features have been the same since their creation. Scientists all around the world were seeing evidence that indicates these statements are false Scientists all around the world were seeing evidence that indicates these statements are false 15-2

An Ancient, Changing Earth James Hutton and Charles Lyell both had written books pointing out evidence that suggest that earth is very old and is slowly changing. James Hutton and Charles Lyell both had written books pointing out evidence that suggest that earth is very old and is slowly changing.

Lamarck's Evolution Hypotheses In 1809, Lamarck proposed that by selective use or disuse of organs, organisms acquired or lost traits during their lifetime. In 1809, Lamarck proposed that by selective use or disuse of organs, organisms acquired or lost traits during their lifetime. These traits could then be passed on to their offspring. These traits could then be passed on to their offspring. Over time this would lead to a change in a species Over time this would lead to a change in a species

Population Growth In 1798, Thomas Malthus published a book in which he noted that babies were being born faster than people were dying In 1798, Thomas Malthus published a book in which he noted that babies were being born faster than people were dying He said that if the human population continued to grow unchecked, sooner or later there would be not enough space or food for everyone He said that if the human population continued to grow unchecked, sooner or later there would be not enough space or food for everyone Darwin realized that this applied to plants and animals even more strongly. Darwin realized that this applied to plants and animals even more strongly.

Conclusion Darwin developed the idea of evolution by natural selection, but others before and during his time had built essential parts of the theory. Darwin developed the idea of evolution by natural selection, but others before and during his time had built essential parts of the theory.

On the Origin of Species In 1859 Darwin published the results of his work, On the Origin of Species. In 1859 Darwin published the results of his work, On the Origin of Species. What the book said: He proposed the mechanism for evolution which he called natural selection He proposed the mechanism for evolution which he called natural selection Evolution has been taking place for millions of years Evolution has been taking place for millions of years Evolution is continuously taking place in all living things Evolution is continuously taking place in all living things 15-3

Inherited Variation Members of each species vary from one another in important ways This variation exists both in nature and on farms –E–E–E–Examples some plants bear larger fruit, some cows give more milk than others These differences were inherited – passed from parents to offspring.

Artificial Selection Nature provides variation in species and humans selected those variation that they found useful. Nature provides variation in species and humans selected those variation that they found useful. Humans select for breeding only the largest pigs, the fastest horses, or the cows that produce the most milk Humans select for breeding only the largest pigs, the fastest horses, or the cows that produce the most milk

Struggle for Existence In nature members of a species compete to obtain food, living space, and other resources In nature members of a species compete to obtain food, living space, and other resources Predators who are able to kill the most will survive. Predators who are able to kill the most will survive. Prey that can avoid being eaten, fastest or better camouflaged will survive Prey that can avoid being eaten, fastest or better camouflaged will survive

Survival of the Fittest Fitness = the ability of an individual to survive and reproduce in its specific environment Fitness = the ability of an individual to survive and reproduce in its specific environment Adaptation = any inherited characteristic that increases an organism’s chance to survive Adaptation = any inherited characteristic that increases an organism’s chance to survive Organisms with successful adaptations will be better suited to their environment and will be able to survive and reproduce Organisms with successful adaptations will be better suited to their environment and will be able to survive and reproduce

Natural Selection/Survival of the Fittest Only the strongest, best adapted individuals will survive in nature Only the strongest, best adapted individuals will survive in nature Organisms that survive pass down their genes Organisms that survive pass down their genes Over time, natural selection results in changes in the inherited characteristics of a population. Over time, natural selection results in changes in the inherited characteristics of a population. These changes increase a species’ fitness (ability to survive) in its environment These changes increase a species’ fitness (ability to survive) in its environment

Living things have been evolving on Earth for millions of years Evidence Evidence Fossil record Fossil record Geographical distribution of living things Geographical distribution of living things Homologous structures of living organisms Homologous structures of living organisms Similarities in early development, embryology Similarities in early development, embryology

The Fossil Record Fossils = remains of ancient life, and the different layers of rock had been formed at different times during Earth’s history Fossils = remains of ancient life, and the different layers of rock had been formed at different times during Earth’s history Fossils act as a record of the history of life on Earth Fossils act as a record of the history of life on Earth

Countless species had lived for a time, and then vanished Countless species had lived for a time, and then vanished By comparing fossils from older rock layers with fossils from younger layers, scientists could document the fact that life on Earth has changed over time By comparing fossils from older rock layers with fossils from younger layers, scientists could document the fact that life on Earth has changed over time

Geographic Distribution of Living Species The existence of similar but unrelated species Animals living in the same ecosystem on different continents were different but had the same anatomies and behaviors b/c they were living in similar ecological conditions they were exposed to similar pressures of natural selection

Homologous body structures Homologous structures = have different mature forms but develop from the same embryonic tissues Homologous structures = have different mature forms but develop from the same embryonic tissues The limbs of reptiles, birds and mammals – arms, wings, legs, and flippers are all very different, but they are all made from the same basic bones The limbs of reptiles, birds and mammals – arms, wings, legs, and flippers are all very different, but they are all made from the same basic bones

Similarities in Embryology The early stages, or embryos, of many animals with back bones are very similar The early stages, or embryos, of many animals with back bones are very similar The common cells and tissues, growing in similar ways leads to homologous structures The common cells and tissues, growing in similar ways leads to homologous structures

Conclusion! All this evidence supports the idea that… All this evidence supports the idea that… Organisms have and still are changing with time Organisms have and still are changing with time A common ancient ancestor A common ancient ancestor