Evolution Overview

Evolution Evolution is change over time Evolution is change over time It was first studied by Charles Darwin (1831) It was first studied by Charles Darwin (1831) He travelled on the HMS Beagle to the Galapagos Islands and came back with many samples of the diverse species He travelled on the HMS Beagle to the Galapagos Islands and came back with many samples of the diverse species He noticed that the species varied from island to island He noticed that the species varied from island to island This lead to his theory of evolution This lead to his theory of evolution

Evolution One of Darwin’s most important insigts was that members of each species vary from one another in important ways. One of Darwin’s most important insigts was that members of each species vary from one another in important ways. Ex.) some plant species bear larger fruit than others Ex.) some plant species bear larger fruit than others From breeders, he learned that some of that idea was heritable variation- meaning differences are passed from parents to the offspring  caused by variation in the genes From breeders, he learned that some of that idea was heritable variation- meaning differences are passed from parents to the offspring  caused by variation in the genes

Artificial Selection This idea came from the idea that breeders select only the “best” This idea came from the idea that breeders select only the “best” Artificial Selection  nature provides the variation and humans select the variations they find the most useful. Artificial Selection  nature provides the variation and humans select the variations they find the most useful. Ex.: horses, dogs, crops, etc. Ex.: horses, dogs, crops, etc.

Natural Selection A process that takes place without humans controlling it or the direction of it A process that takes place without humans controlling it or the direction of it Involves the idea of “survival of the fittest”, “struggle for existence”, adaptation, and fitness. Involves the idea of “survival of the fittest”, “struggle for existence”, adaptation, and fitness.

Struggle for Existence High birth rates among animals and a shortage of life’s basic needs forces organisms into a competition for resources High birth rates among animals and a shortage of life’s basic needs forces organisms into a competition for resources This includes: food, living space, and other necessities This includes: food, living space, and other necessities Predator-Prey relationship Predator-Prey relationship

Fitness A key factor in the struggle for existence is how well suited an organism is to its environment. A key factor in the struggle for existence is how well suited an organism is to its environment. The ability of an individual to survive and reproduce in its specific environment is called fitness. The ability of an individual to survive and reproduce in its specific environment is called fitness.

Adaptation Any inherited characteristic that increases an organism’s chance of survival. Any inherited characteristic that increases an organism’s chance of survival. Enable organisms to become better suited to their environment and this better able to survive and reproduce Enable organisms to become better suited to their environment and this better able to survive and reproduce Can be anatomical, structural characteristics, physiological process, and behavior Can be anatomical, structural characteristics, physiological process, and behavior

Survival of the Fittest Idea that individuals with characteristics that are no well suited to their environment (low levels of fitness) either die or leave few offspring. Individuals that are better suited to their environment (have adaptations that enable fitness) survive and reproduce most successfully Idea that individuals with characteristics that are no well suited to their environment (low levels of fitness) either die or leave few offspring. Individuals that are better suited to their environment (have adaptations that enable fitness) survive and reproduce most successfully

Main Point of Natural Selection Overtime, natural selection results in changes in the inherited characteristics of a population. These changes increase a species’ fitness in its environment. Overtime, natural selection results in changes in the inherited characteristics of a population. These changes increase a species’ fitness in its environment.

Descent with Modification Over long periods of time, natural selection produces organisms that have different structures, establish difference niches, or occupy different habitats. As a result, species today look different from their ancestors. Each living species has descended, with changes, from other species over time. Over long periods of time, natural selection produces organisms that have different structures, establish difference niches, or occupy different habitats. As a result, species today look different from their ancestors. Each living species has descended, with changes, from other species over time. This idea leads to the other idea that all living organisms are related to one another and is known as common descent. This idea leads to the other idea that all living organisms are related to one another and is known as common descent.

Evidence for Evolution Darwin suggests that all living things have been evolving on Earth for millions of years. Darwin suggests that all living things have been evolving on Earth for millions of years. Evidence can be found: Fossil record, geographical distribution of living species, homologous structures of living organisms, and similarities in embryology. Evidence can be found: Fossil record, geographical distribution of living species, homologous structures of living organisms, and similarities in embryology.

Fossil Record By comparing fossils from older rock layers with fossils from younger rock layers, you can document the fact that life on Earth has chaged over time. By comparing fossils from older rock layers with fossils from younger rock layers, you can document the fact that life on Earth has chaged over time. Youngest fossils are found closest to the top of the earth’s crust, and oldest farther down Youngest fossils are found closest to the top of the earth’s crust, and oldest farther down There are gaps in the fossil record, but that proves the idea that we still don’t know how certain organisms have evolved. This changes everyday that new fossils are found. There are gaps in the fossil record, but that proves the idea that we still don’t know how certain organisms have evolved. This changes everyday that new fossils are found.

Geographic Distribution Species now living on difference continents had each descended from different ancestors. However, because some animals on each continent were living under similar ecological conditions, they were exposed to similar pressure of natural selection. Because of those similar pressures, different animals ended up evolving certain striking features in common. Species now living on difference continents had each descended from different ancestors. However, because some animals on each continent were living under similar ecological conditions, they were exposed to similar pressure of natural selection. Because of those similar pressures, different animals ended up evolving certain striking features in common.

Homologous Body Structures Amongst species, certain structures have different forms but develop from the same embryonic tissues. They have the same basic structure but different functions. Amongst species, certain structures have different forms but develop from the same embryonic tissues. They have the same basic structure but different functions. Ex. Bird Wings and Reptile limbs or Bat Wings and human Hands Ex. Bird Wings and Reptile limbs or Bat Wings and human Hands

Vestigial Structures Not all homologous structures serve important functions. The organs of some animals are so reduced in size that they are traces of homologous organs in other species. These are known as vestigial structures. Not all homologous structures serve important functions. The organs of some animals are so reduced in size that they are traces of homologous organs in other species. These are known as vestigial structures.

Embryology The embryos of many animals with backbones is very similar. The embryos of many animals with backbones is very similar. It is clear that the same groups of embryonic cells develop in the same order and in similar patterns to produce the tissues and organs of all vertebrates. These common cells and tissues, growing in similar ways, produce the homologous structures! It is clear that the same groups of embryonic cells develop in the same order and in similar patterns to produce the tissues and organs of all vertebrates. These common cells and tissues, growing in similar ways, produce the homologous structures!

Speciation

Isolating Mechanisms Reproductive Isolation Reproductive Isolation Behavioral Isolation Behavioral Isolation Geographical Isolation Geographical Isolation Temporal Isolation Temporal Isolation