founder of modern evolutionary theory 1831 darwin became a naturalist on the hms beagle studied...

• Founder of modern evolutionary theory

• 1831 Darwin became a naturalist on the HMS Beagle

• Studied animal and plant life on mapping expedition to South America and South Pacific

• Darwin studied anatomy of insects, reptiles, birds and flowering plants

Galapagos Tortoises• The inhabitants...state that they

can distinguish the tortoise from different islands; and that they differ not only in size, but in other characters. Captain Porter has described those fromCharles and from the nearest island to it, namely Hood Island, as having their shells in front thick and turned up like a Spanish saddle, whilst the tortoises from James Island are rounder, blacker, and have a better taste when cooked.---Charles Darwin 1845

• That there must be a struggle for existence among all individuals

• Organisms must struggle for– Food– Space– Prey

• From ancient times, most people believed all living things were created by a divine being at the same time and remained unchanged.

• By the time Darwin set sail, numerous discoveries, including a rich fossil record, had turned up importance evidence that caused some scientists to question these ideas.

• Geologists James Hutton and Charles Lyell– After examining Earth in great detail, recognized

that Earth is many millions of years old, and the processes that changed Earth in the past are the same processes that operate in the present.

– Ex: volcanoes, earthquakes, erosion, continental drift, etc.

The Grand Canyon, with its many layers of rock, was formed over millions of years by the Colorado River (erosion).

• Jean-Baptiste Lamarck - French naturalist– Published hypothesis of Inheritance of

Acquired Characteristics same year Darwin was born

– Proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime.

• Traits could then be passed on to offspring• Over time would lead to change in species

• Thomas Malthus - English economist– Reasoned that if the human population

continued to grow unchecked, eventually there would not be enough space and food for everyone

• Forces such as war, famine and disease work against the growth

– Darwin realized this was even more true for plants and animals because humans produce far fewer offspring

• Upon returning to England, Darwin began studying his specimens and filling notebooks with ideas.

• Shared ideas with friends but reluctant to publish -- understood his ideas challenged scientific and religious beliefs of his day

• After more than 25 years -- published On the Origin of Species in 1859

Charles Darwin Published:“On the Origin of Species”

Only some of the population survive long enough to produce offspring

• Darwin’s observations led to the conclusion that individuals have different variations of traits that can be inherited

Darwin bred pigeons with desirable variations and he was able to produce offspring with the same features

• Breeder selects the particular traits

• Darwin wondered if there was some force in nature similar to artificial selection

•NATURAL SELECTION

• Mechanism for change in populations that occurs when organisms with favorable variations for a particular environment survive, reproduce and pass variations on to the next generation

• Organisms with less favorable variations are less likely to survive and pass on traits to the next generation

Tendency toward Overproduction

• For example: Fish lay thousands of eggs

• Most of these eggs will not survive

Individuals Exhibit Variations

• Example: Fishes may differ slightly in color, fin and tail size and speed

Individuals with favorable traits survive and pass on those genes• Ex: A fast fish with

camouflaged skin will be more likely to survive and reproduce. Thus, passing along the more desirable traits to future offspring.

Populations evolve, or change over time

• Gradually, the offspring of the survivors make up a larger portion of the population. After many generations the population may look entirely different.

• Changes in structure or body parts that aide in survival

• To copy the appearance of another species

• Color adaptation so organism blends with its surroundings

• May take millions of years to develop or they may be rapid

• Ex: Slow---Sightless mole rat

• Fast: Antibiotic resistance

• Fossils show change over time

The Fossil Record

• Geographical Distribution– Organisms live in different areas of the world,

but have similar adaptations– Different ancestors, but similar environmental

pressures acting against it

• Descent with modification

• Modified structure that is seen among different groups of descendants

• Similar in function, but different in structure

• Ex: Bird Wing/Butterfly Wing

• Any body structure that is reduced in function in a living organism but may have been used in an ancestor

• Fish, reptiles, birds and mammals look similar during embryological development

• Speciation, or the formation of new species, can only occur when either interbreeding or the production of fertile offspring is somehow prevented: Reproductive Isolation– Geographic isolation– Temporal isolation– Behavioral Isolation

• Occurs when two populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior.

• Ex. Eastern and Western Meadowlarks– Habitat overlaps, but will not mate with each

other because they do not respond to each others song!

• Two populations are separated by geographic barriers such as rivers, mountains, or bodies of water.

• Ex. Colorado River separating the Abert squirrel and the Kaibab squirrel (about 10,000 years ago).

• Two or more species reproduce at different times.

• Example: Orchids. Release pollen on different days, so they cannot pollinate each other.