Scientists explore the concept of evolution Evolution ~ a gradual change over time “The process through which species change over time” This change is a result of the change in the genetic material of an organism and is inherited (passed from one generation to the next)

Scientists explore the concept of evolution Early Ideas Early 1700s: scientists could see species change over time…but how Jean-Baptiste de Lamarck: French, early 1800s proposed that species have changed over time Based on the idea an individual organism can acquire a new trait during a lifetime and pass it down Ex: giraffes stretched their necks to reach leaves, passing this trait for long necks to their offspring What is missing here? Evidence!

Scientists explore the concept of evolution Darwin’s Observations (1809-1882) Spent 5 years on board the Beagle: sailed from England, along the coast of South America – studied rock formations, fossils, and life 18 Galapagos Islands: plants and animals not only differed from those on the mainland, but also between islands Alfred Russel Wallace – proposed similar ideas around the same time

Darwin’s Observations Observed several types of tortoises on the islands Short necks in damp areas with plentiful plant life Longer necks in dry areas with cacti Finches, beak shapes and sizes Heavy, short beaks for pecking trees Small, thin beaks for capturing insects

Natural Selection explains how living things evolve Darwin struggled to develop an explanation that would account for the diversity he saw Breeders can produce new variations of an animal over time: artificial selection New breed: select dogs with a certain trait – mate Resulting litter: again selectively breed…until a new breed is produced

Natural Selection Explains how Things Evolve Darwin: Similar process occurring in nature: Natural Selection – members of a species that are best suited to their environment survive and reproduce at a higher rate than other members of the species Based on: overproduction, variation, adaptation, and selection * both artificial and natural selection have similar results: desired results are passed from one generation to the next…they differ in that humans control one process and the other is due to natural processes *Theory: a well-tested explanation based on a broad range of facts and observations – not proven, but are generally accepted to be true

Natural Selection explains how living things evolve Population: group of individuals of the same species that live in a particular environment or area Overproduction: A plant or animal that reproduces usually makes more offspring than can possibly survive (than the environment can support): Ex: several thousand salmon eggs, not all hatch, a few hundred survive disease or predation, several dozen reach adulthood, and few will successfully reproduce Variation Species have natural differences/variations in traits – ex: fin size These are passed on from one generation to the next Genetic material may change – new variation (mutation) Reproduction: passes these traits to offspring Adaptation A mutation can make an individual better able to survive An advantage in the particular environment; ex: tail shape – swim faster Selection Particular adaptations lead to survival long enough to reproduce That adaptation becomes more common in the next generation of offspring Genetic variation: differences in DNA in a population Environmental factors: conditions that affect survival – include food supply, habitat, predators, and disease

Darwin’s Theory of Evolution by Natural Selection basic idea – “Descent with modification” Although some details were absent (or under-developed because he couldn’t know, for example, the structure of DNA and the mechanism of inheritance), Darwin’s fundamental ideas have been supported by overwhelming evidence from morphological, biochemical, fossil, behavioral, and direct observational data

New species develop from earlier species In 1859, after more than 20 years of work, Darwin published, On the Origin of Species Speciation: Evolution of new species from an existing species Environmental changes (rapid or gradual) Ex: in book Lake Tanganyika: over 150 cichlid species pB24

New Species Develop from Earlier Species Isolation: Darwin’s trip to the Galapagos: islands were separated from the mainland by miles of ocean, ad unable to breed with mainland relatives New species evolved Darwin: isolation of population by geographical or other barriers could contribute to the process of speciation Today: isolation is essential to speciation – for species to separate, two populations must be prevented from reproducing with each other Geographic boundary – ocean, mountain range, feed on different things, reproduce at different times of the year Mutations in one isolated group may differ from another…two populations may evolve differently from each other  Speciation  BIODIVERSITY on Earth