Evolution and Natural Selection - PowerPoint Presentation

Slide1

Evolution and Natural Selection

Change over time…Slide2

Geology

Began to study rock layers called strata

George Cuvier

Studied fossilsFound extinct species and noticed the deeper the fossil the more uniqueCatastrophismCharles LyellBelieved the earth to be millions of years oldUniformitarianismSlide3

Jean

Baptiste

Lamarck

In 1809, Lamarck proposed that organisms evolved into more and more complex forms through use and disuse and the inheritance of acquired characteristicsOrganism strived to improve, causing new body structures to develop and “unused” structures to disappearUsed structures would pass on to the offspringThis theory is NOT accepted todaySlide4

Charles Darwin and the Beagle

In 1831, at the young age of 21, Charles Darwin took a job as a naturalist on the British ship know as the H.M.S. Beagle

On his five year journey Darwin studied and collected many different organisms

When Darwin arrived at the Galapagos Islands, he was intrigued by the odd variety of species he saw thereSlide5

The Galapagos Islands

This small group of islands is home to many unique creatures, such as the giant tortoise, large marine iguanas, and flightless birds know as the cormorant

In particular, Darwin noticed that there were many varieties of finches. Each variety was similar to the finches of the mainland of South America, yet adapted to its environment in a unique way.

ADAPTATION – Any inherited characteristic or behavior that helps an organism better survive in its environmentSlide6

The Origin of Species

When Darwin returned to England, he took his findings and compiled them into a book. It was not until another scientist, Alfred Wallace, approached him with his findings of how evolution worked that Darwin would publish his work.

In 1859, Darwin published The Origins of Species, By Means of Natural Selection

He stated that evolution occurred through natural selection.Slide7

Natural Selection

Darwin proposed that natural selection caused species to change

Overproduction -

Organisms produce more offspring than can survive, Genetic Variation - There is variationStruggle to Survive - Some variations help the organism survive better in its environment. (Competition over food, mates, shelter, water, etc.)

Differential Reproduction

– Individuals with the best traits reproduce more. Over time more individuals will have the favored trait. Therefore, the population gradually changes, evolves, over time to better suit its environment.

Survival of the fittest

Fitness is a measure of an individual’s hereditary contribution to the next generation.Slide8

Adaptations

Fitness-

a measure of an organisms contribution of viable offspring to the next generation

Camouflage – adaptation that allows for blending in with the environmentMimicry – one species evolves to look like another speciesAntimicrobial resistance – “Super” bacteria; bacteria that are resistant to most antibioticsSlide9

Do Now

Who is Lamarck? What did he do?

Lamarck was one of the first scientist to proposed evolution. He believe that traits could be acquired throughout a life time and passed on to offspring. Anything that an organism did not use during that lifetime would be lost, hence his theory of acquired characteristics through use and disuse.

What is an adaptation?Any inherited characteristic or behavior that helps an organism better survive in its environmentWhat are the 4 aspects of natural selection?Over reproduction

Variation among the species

A struggle for survival – some are better suited than others and will survive to reproduce

Inheritable traits meaning that the more favorable traits are passed on and begin to become a larger portion of the populationSlide10

Evidence for Evolution

Darwin’s theory is supported by many different types of scientific evidence

Fossils clearly show that many species have changed over time; some fossils show transitional forms (intermediate species between old and new species)

Derived v. Ancestral TraitsNew traits v. oldFeathers v. teeth Slide11

Evidence for Evolution - Structures

Homologous structures

– many species with common ancestry show similar structures. Ex: forelimbs have similar bone structure

Analogous Structures – unrelated species living in similar habitats often have similar structures. Ex: shark and dolphin fins/ bird and insect wingsVestigial Structures – a structure that no longer serves a purpose. Ex: appendix (humans) or pelvic bone (whales)Slide12

Comparative Embryology and Genetics and Biogeography

Genetic evidence

– today, similarities in DNA and amino acid sequences show how species are related. Ex: humans and chimpanzees (our closest living relative) share over 90% of our DNA

Embryology –vertebrates share similar characteristics at early stages of developmentBiogeography – the distribution of plants and animals effects how natural selection works on themSlide13

Patterns of Evolution

Isolation and natural selection can lead to different types of evolution

Convergent evolution

– distantly related organisms become more similar over time due to similar habitatsDivergent evolution – one species eventually diverges into two or more species, becoming increasingly different over time in response to different environmentsAdaptive radiation Artificial Selection – Humans choose the traits that they want which leads to evolution as well

Coevolution

– when two interacting species evolve around each other (predator/prey; host/virus; plant/pollinator)Slide14

Isolation

Speciation often begins when two groups become isolated

Two types of isolation

Geographic isolation – a physical barrier separates 2 groups, such as a body of water, mountain range, highway etc.Reproductive isolation – occurs when 2 groups cannot reproduce together; sometimes caused by geographic isolation, but can also occur because of a change in behaviorPrezygotic isolation Postzygotic isolationSlide15

Species

The process of species formation is called

speciation.

For many years species were determined by morphology, the internal and external appearance of an organism.

The morphological concept of species has limitations since individuals within a species can look different.

The

biological species concept

says that a species is a population that can interbreed but cannot breed with other groups.

Modern day definition states that a

species is one

that looks similar and allows for interbreeding to produce fertile offspringSlide16

Non-Random

Matings

Stabilizing selection

is when the individuals with the average form of the trait have the highest fitness.Directional selection is when the individuals with a more extreme form of the trait have greater fitness than the average form of the trait.Disruptive selection

is when the individuals with either form of the extreme trait have greater fitness than the average form of the trait.

Sexual selection

is when one mate has to chose the other based on certain characteristics.Slide17

Biodiversity

Evolution usually leads increased biodiversity

Increased biodiversity strengthens an ecosystem by increasing the “connections” in the food web and making it less susceptible to disease

If species cannot evolve quickly enough, evolution may lead to extinctionThere have been 5 mass extinctions throughout historyAre humans currently causing the next mass extinction?