What does this picture mean to you?
Changes Over Time Cells and Heredity Chapter 5
Charles Darwin 1809 – 1892 A naturalist (studied plants and animals by observing them in their natural habitat) aboard the HMS Beagle in 1831 Believed that favorable variations in an organism, no matter how slight, enabled the organism to survive and pass the trait to offspring
Darwin’s Observations Darwin observed that organisms on the Galapagos island were similar to those on the mainland of South America and were similar to those on neighboring islands. Variation: a slight difference in an inherited trait of individual members of a species –Variations are caused by random mutations in an organisms DNA which cause differences in phenotypes within a population
Darwin’s Theory of Natural Selection Natural Selection: a theory of how evolution occurs; a process where individuals that are better adapted to their environment are more likely to survive and reproduce Factors that affect natural selection: variation, overproduction, and competition
Adaptations Adaptations: an inherited trait that helps an organism survive and reproduce –Camouflage – enables an organism to blend in with its environment –Mimicry – resemblance of one organism with another
Darwin’s Finches
These drawings are of four species of finches on the Galapagos island. Beak size and shape indicate the type of food each species is adapted to eating.
Overproduction In some species, many more offspring are born than will survive. This ensures that some will survive to adulthood, passing on the favorable traits to the next generation.
Variations in a species: Can you spot the variation in coat pattern on these zebras?
Competition Too many organisms that occupy the same niche will have to compete for available resources. Only the best adapted will survive long enough to reproduce.
Selection Some variations make an organism better adapted to its environment. The alleles for these variations are more likely to be passed on to the next generation. Thus, natural selection can lead to evolution.
Evolution Evolution: the gradual change in a species over time –Species: a group of similar organisms that can mate with each other and produce fertile offspring
Artificial Selection Breeding of organisms for desired traits
How do new species form?
Geographic Isolation Geographic Isolation: individuals of a species become separated from the rest of the species long enough to develop markedly different characteristics This separation is from land masses, bodies of water, or other geographic structures.
Pangea Continental Drift: Pangaea separated into the continents we have now, separating groups of a species
Evidence for Evolution Scientists have combined evidence from fossils, body structures, early development, and DNA and protein sequences to determine evolutionary relationships among species. Comparative Anatomy – the study of similarities and differences among structures of living species
Comparative Anatomy Homologous Structures: similar structures in similar positions with different functions In this figure, the similar bone structures can be seen between these vastly different organisms
Comparative Anatomy Analogous structures – body parts that perform similar functions but differ in structure
Vestigial Structures Vestigial Structures – body parts that have lost their original function through evolution
Similarities in Early Development In early development, many organisms share characteristics, like tails and gill slits Embryology – the science of the development of embryos from fertilization to birth
Similarities in DNA DNA sequences of related organisms are more similar than DNA sequences of non-related organisms.
Branching Tree Branching Tree: a diagram that shows how different groups of organisms are related. Those organisms on closer branches are more closely related.
Evolutionary Theories Punctuated Equilibrium: the theory that evolution occurs in short rapid bursts separated by long periods of no change Gradualism: the theory that evolution is a slow and continuous process