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Adrienne Towns

on 24 January 2016

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Transcript of Evolution

Background photo by t.shigesa
Darwin and his findings
Collected data while traveling the Galapagos Islands that helped him form his hypothesis for evolution
Noted the diversity of the islands and how organisms were suited for their environment
Collected fossils and saw that ancient organisms resembled present organisms
Evidence for Evolution
1) Fossil Record
2) Biogeography
3) Homologous Body Structures
4) Similarities in Embryology
5) Genetics and Molecular Biology
Other Mechanisms of Evolution
Background Information
Evolution: theory that states modern organisms descended from ancient organisms with modifications
Theory= well-supported testable explanation of things that happen in the world
Stated that organisms use and disuse of characteristics lead to loss or gain of traits during their lifetime
These traits could be passed on to offspring
Eventually it would cause the species to change
Key points:
Darwin's Case
Published "On the Origin of Species"
struggle for existence- organisms compete for resources
more offspring produced than can survive
limited resources= differential reproductive success
some organisms survive to reproduce and pass on traits and others die

Fossil Record
Orderly representation of organisms from the past, but incomplete
Oldest fossils on lower layers of rock (chronological order)
Used for dating organisms
Shows that organisms evolve gradually or rapidly and not all changes are documented
Species on different continents evolved from a common ancestor based on ecological conditions and selective pressures
Relates back to Pangea and it breaking apart
Body Structures
Structures in organisms that have different mature forms but develop from the same embryonic tissue
anatomically same, different functions
Evidence of evolution in living things
Embryos look and develop similarly during early stages of development
Summary of Darwin
organisms differ and these characteristics are heritable
organisms produce more offspring than can survive
compete for resources
Strengths and Weakness of Evolution
Have lots of biological, geological, and physical data to support Darwin's hypothesis
Same data contradicts it, but discrepancy's are few
Technology and further research continue to modify the theory
Besides natural selection there are 4 other mechanisms of evolution in populations
gene shuffling (recombination)
genetic drift
gene flow
Change in sequence of DNA
replication mistakes
environmental factors
Do not always affect phenotype
A source of genetic variation through sexual reproduction
Some can effect an organisms fitness
Gene Shuffling (Recombination)
shuffling (recombining) of genes during gamete formation
during meiosis, independent assortment & crossing-over
source of genetic variation
Genetic Drift
Random change in allele frequencies that occurs in small populations
Can cause founder effect
change in allele frequencies due to migration of a small subgroup of a population
Since this is by chance it does not produce adaptations
Gene Flow (Migration)
Movement of genes between populations
May happen through the migration of organisms or the movement of gametes
ex: pollen blown to a new location
Evolution Recap
Process by which organisms have descended from a common ancestor
Descent w/ modification and the genetic differences that are heritable and passed on to the next generation
Evolution of Cells
Eukaryotes have evolved from prokaryotic cells
Endosymbiotic theory: eukaryotic cells formed from a symbiosis among several different prokaryotic organisms
Influenced by:
Hutton and Lyell- Earth is millions of years old, same processes happen today as in the past
Malthus-human population will out grow resources (relates to any population)
Lamarck-hypothesized the inheritance of acquired traits
Tendency toward perfection: organisms change over their lifetime to achieve complexity and perfection
Use and Disuse: if an organ was used a lot it would increase in size and if not used it would decrease
Inheritance of acquired traits: a trait gained during organisms lifetime can be passed on to offspring
Natural Selection
natural selection (survival of the fittest)- organisms best suited for the environment live to reproduce
called fitness
adaptations- characteristics that increase an organism's chance of survival creating genetic diversity in a population
natural selection=changes of inherited characteristics of a population that increase a species' fitness
natural selection leads to descent with modification
overtime species have changed from their ancestor
Sudden appearance
Fossils do not show gradual descent with modification, but change all at once
Fossils show little to no change looking the same as they did when they disappeared
Sequential nature of groups
species change in an orderly manner
Species in on location moved to other locations leaving behind related species and ancestors
All 4 limbed vertebrates have descended with modification from common ancestors
Vestigial organs: traces of homologous structures that are reduced in size, with some not used
Groups of embryonic cells develop in the same order and similar pattern produces in vertebrates
these commonalities produces homologous structures
Genetics & Molecular
All organisms have the same nucleic acids
Differences come from order of nucleotides
Similarities in genetic code of all organisms
Process of replication and protein synthesis is similar in all organisms as well
Homologus proteins- proteins that are very similar in structure and chemical make-up
Cytochrome C- protein used in cellular respiration
Hox genes- protein used in early embryonic development to determine head-to-tail axis
organisms have advantages and disadvantages in struggle for existence
those best suited for environment survive and reproduce passing on advantages traits, other die
Species today descended with modification from ancestral species in the past
Mutation, migration (gene flow), genetic drift, and natural selection are mechanisms of evolution
Darwin developed the hypothesis for natural selection
Variation+differential reproduction+heredity= evolution by natural selection
Genetic variation is necessary for population changes
mitochondria & chloroplasts resemble bacterial structure
mitochondria & chloroplasts have their own circular DNA, like bacteria
mitochondria & chloroplasts move freely within the cell
mitochondria & chloroplasts reproduce independently from the cell (binary fission)
Full transcript