Idea of Evolution

Charles Darwin (1809-1882) English naturalist Took a trip around the world on a ship called

H.M.S. Beagle Mostly fascinated with the Galapagos Islands Best known for his theory of evolution by

natural selection

Idea of Evolution

Galapagos Islands Groups of animals vary from island to island

Ex: tortoises on each island resemble each other but differ in the shape and function of their shells

Ex: finches on each island resembled each other but differ in the shape and function of their beaks

Darwin believed these unique animals all came from a common ancestor and they changed/adapted to their environment

Idea of Evolution

Evolution Development of new types of organisms over

time Heritable change in the characteristics within

a population from one generation to the next

Ideas of Darwin’s Time

Scientists thought all species were permanent and unchanging

The Earth was believed to only be a few thousand (not billions) of years old

Charles Lyell was a English geologist that believed the Earth’s surface continues to change Influenced Darwin

Ideas of Darwin’s Time Jean-Baptiste Lamarck

French biologist that supported the idea that populations of organisms change over time

Also believed in biogenesis of simple organisms

Proposed that individuals acquire traits during lifetime from behavior and pass them onto offspring Called Theory of Acquired Traits

Darwin’s Ideas Around the same time Darwin and Wallace

formed theory to explain evolution

Published book On the Origin of Species in 1858 Book explained how evolution occurs by

means of natural selection

Descent with Modification Idea that every species must have

descended by reproduction from pre-existing species that arrange over time Ex: finch beaks at Galapagos

Natural Selection

Mechanism from descent with modification 1. Overproduction

More offspring are produced than survive to maturity

2. Genetic variation Traits vary within a

species Ex: deer fur

thickness is passed on to future offspring

Natural Selection (cont’d) 3. Struggle to survive

Organisms need to compete with each other known as “struggle for existence”

When an organism is successful in a new environment its called an adaptation

4. Differential Reproduction Organisms best

adapted for an environment will survive best and reproduce

Survival of the fittest The ability for an

organism to reproduce and pass on adaptations

The Fossil Record

Fossils Remains of an organism

that died long ago Some are remains of

extinct organisms, meaning the species is no longer alive

Superposition Idea that strata form in

layers where the layers closest to the top are the younger than below

The Fossil Record Relative Age

Age compared to other fossils in order of old to young

Absolute Age Using radiometric dating to get actual number age

The Fossil Record

Scientists use these relative and absolute ages to try and make the history of life on Earth as precise as possible

Fossil records are incomplete history because not all organisms have left fossils behind Fossils can easily be

destroyed during the process Finding fossils is rare also

Transitional Species We can infer that species have gradually

changed based on the fossil record Scientists have hypothesized ancestors and later

descendant species

Organisms with features that are between hypothesized ancestors

Biogeography Study of locations of organisms around the

world

Darwin used this method when exploring islands and observed animals variation based on environment

Anatomy and Embryology

Anatomy: study of the body

Embryology: study of development

Homologous structures Anatomical structures that

originated by heredity from a structure in most common ancestor Ex: bones in arms of humans,

penguins, alligator and bat Related structure but function

may differ

Anatomy and Embryology

Analogous Structures When structures have

similar function, but did not develop the same way Ex: wings of bat vs.

bird

Vestigial Structures Organs that no longer

serve a function in an organism

Ex: human tail bone, appendix

Phylogeny

Relationships among groups of organisms

Can make a “tree” of animals evolved Trunk of the tree would

represent species that are closely related

Branches represent a separate population or lineage

Caribbean Anole Lizard

Found in the Caribbean islands of Cuba, Hispaniola, Jamaica, and Puerto Rico Each lizard species body type differs by their habitat

Ex: stocky body and long legged lizards are best adapted for tree truck environments, slender bodies and long tails are best adapted for grassy environments

Hypothesis #1: An ancestral anole species specialized for living on twigs originally lived on one island and later migrated to other islands

OR

Hypothesis #2: Each twig-dwelling species evolved independently on each island from distant ancestor anole species

Evolution in Action

Biologists tested the hypothesis by comparing DNA from the various species DNA evidence supported hypothesis 2 that

each lizard evolved independently on each island

Convergent Evolution Process by which different species

evolve similar traits Ex: sugar glider of Australia and flying

squirrel of North America came from different ancestors but evolved similar adaptations to their environment

Divergence & Radiation Divergence evolution

Process by which the descendants of a single ancestor diversify into species that each fit different parts of the environment Ex: lizards with genes for large toe pads and

short legs ran slowly on the tree trunks and fell easily to predators, lizards with long legs and small toe pads were able to slip away and reproduce

Divergence & Radiation

Adaptive Radiation Pattern of variation when a new population in

a new environment undergoes divergent evolution

Artificial Selection Process the occurs when

human breeders choose individuals that will parent the next generation Ex: faster greyhounds, smaller

tea cup dogs, high milk yield cows, high yielding grain per stalk

Darwin hypothesized domesticated dogs diverged from wolves DNA evidence indicated

similarities with wolves in East Asia, supporting Darwin’s hypothesis and humans selected domestic dogs from wolf population 15,000 years ago

Coevolution

Evolution is on-going and many species may evolve together

Coevolution When two or more species have evolved

adaptations to each other’s influence

Predator/Prey Interactions

Introduction of new species

Creating antibiotics