Evolution
Where did all the diversity come from? Evolution change over time; the process by which modern organisms have descended from ancient organisms Charles Darwin contributed to the theory of evolution more than anyone else
Theory of Evolution Evolution of man Charles Darwin Father of Evolution
Darwin s Observations Enormous number of species inhabit the Earth Organisms are well suited to their environment Why did some species live in the same ecosystems that others do not?
Observations con t. Darwin collected preserved remains of ancient organism, called fossils Some fossils resembled living organisms, while some looked completely different
Galapagos Islands The islands all have very different climates Small, lower islands were hot, dry, and nearly barren Higher islands more rainfall and numerous fauna and flora Fascinated with the land tortoises and marine iguanas Most famous research Darwin s finches (beaks)
Galapagos Organisms Galapagos Tortoise Galapagos Finches
Homeward Bound The characteristics of many animals and plants varied noticeably among the different islands of the Galapagos Could these species, which now live on different islands, be related through a common ancestral species?
Evolution ORIGIN OF EVOLUTIONARY THOUGHT
Ideas Shaping Darwin Early thought was that the Earth and all its forms of life were created a few thousand years ago In that short time life could not have changed Fossils records began to challenge this thought however
Lamarck s Hypotheses - 1809 Proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime These could then be passed on to their offspring, which over time led to a change in species
Lamarck con t. Movement to Perfection All organisms move toward complexity and perfection They are continually changing and acquiring features that help them live more successfully in their environments Use and Disuse Organisms could alter the size and shape of particular organs by using their bodies in new ways Inheritance of Acquired Traits Ex. Lift muscles to build muscles -> children big
Evolution DARWIN S THEORIES
Origin of Species In 1858, Wallace sent Darwin his thoughts on evolutionary thought In 1859, Darwin published On the Origin of Species
Struggle for Existence Members of each species compete regularly to obtain food, living space, and other necessities of life A key factor is an individual s FITNESS an individual s ability to survive and reproduce in a given environment
Existence con t. Fitness results from ADAPTATIONS Can be anatomical, physiological, or behavioral
Survival of the Fittest Individuals with characteristics that are not well suited to their environment those with low levels of fitness either die or leave few offspring Individuals that are better suited to their environment adaptations that enable fitness survive and reproduce most successfully
Which is MORE fit for their environment?
Environment - Desert
Environment - Grasslands
Environment - Arctic
Natural Selection Darwin referred to Survival of the Fittest as NATURAL SELECTION Traits that are selected contribute to an organism s fitness in the environment This results in the changes in the inherited characteristics of a population
Descent with Modification Over long periods, natural selection produces organisms that have different structures, establish different niches, or occupy different habitats That s why species today look different from their ancestor This theory leads to the idea of COMMON DESCENT all species living and old were derived from a common ancestor
Ancestral Horse
Structural Evidence of Evolution Homologous Structures Structures that have different mature forms but develop from the same embryonic tissues Ex. Limbs of reptiles, birds, and mammals arms, wings, legs, and flippers All vary greatly in form and function but are constructed from the same basic bones
Homologous Structures
Structural Evidence con t. Vestigial organs Organs of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs in other species These do not affect an organism s ability to survive and reproduce
Embryonic Similarities Early stages, or embryos, of animals with a backbone are very similar Same groups of embryonic cells develop in the same order and pattern to produce the tissues and organs of all vertebrates
Embryos