evolution and natural selection
DESCRIPTION
Evolution and Natural Selection . Change over time…. Geology. Began to study rock layers called strata George Cuvier Studied fossils Found extinct species and noticed the deeper the fossil the more unique Catastrophism Charles Lyell Believed the earth to be millions of years old - PowerPoint PPT PresentationTRANSCRIPT
EVOLUTION AND NATURAL SELECTION Change over time…
GEOLOGY Began to study rock layers
called strata George Cuvier
Studied fossilsFound extinct species and
noticed the deeper the fossil the more unique
Catastrophism Charles Lyell
Believed the earth to be millions of years old
Uniformitarianism
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 characteristics
Organism strived to improve, causing new body structures to develop and “unused” structures to disappear
Used structures would pass on to the offspring
This theory is NOT accepted today
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 there
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 environment
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.
NATURAL SELECTION Darwin proposed that natural
selection caused species to change
1) Overproduction - Organisms produce more offspring than can survive,
2) Genetic Variation - There is variation
3) Struggle to Survive - Some variations help the organism survive better in its environment. (Competition over food, mates, shelter, water, etc.)
4) 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 fittestFitness is a measure of an individual’s hereditary contribution to the next generation.
ADAPTATIONS Fitness- a measure of an
organisms contribution of viable offspring to the next generation
Camouflage – adaptation that allows for blending in with the environment
Mimicry – one species evolves to look like another species
Antimicrobial resistance – “Super” bacteria; bacteria that are resistant to most antibiotics
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 environment
What 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 population
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 Traits New traits v. old Feathers v. teeth
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 wings
Vestigial Structures – a structure that no longer serves a purpose. Ex: appendix (humans) or pelvic bone (whales)
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 development
Biogeography – the distribution of plants and animals effects how natural selection works on them
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 habitats
Divergent 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)
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 behavior Prezygotic isolation Postzygotic isolation
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 offspring
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.
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 extinction
There have been 5 mass extinctions throughout history
Are humans currently causing the next mass extinction?