How Biological Diversity Evolves

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Chapter 14

• How Biological Diversity Evolves

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Macroevolution

• Major changes in the history of life
• Evident in the fossils could see the origins of
  new species
• leads to biological diversity
• Origins of evolutionary novelties such wings and
  feathers on birds, big brains in humans
• saw thousands of new plants with the evolution of
  flowers and new mammals once the dinosaurs were
  gone

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Linear vs Branched Evolution

• Linear evolution species change and adapt to a
  new environment without creating a new species
• Speciation occurs during branched evolution
  create a new species because adaptations are very
  different than parent
• increases biological diversity

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Species

• Defined by biological species concept
  population or group of populations whose members
  have the potential to interbreed with one another
  to make fertile offspring
• woman from New York could mate with a man from
  Mongolia if they could get together but she
  cannot mate with a chimpanzee because there are
  blocks on the exchange of genes between species
• Different species may have similarities and the
  same species may have variation
• This only works with sexual organisms asexual
  organisms do not reproduce this way

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Classification

• Based on observable and measurable physical
  traits
• In terms of ecological niches that focus on
  unique adaptations to roles in biological
  communities
• Unique genetic history

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Reproduction Barriers

• What maintains the barriers between closely
  related species?
• 2 skunks have overlapping ranges and is hard to
  tell apart but still remain separate species
• Barriers are either pre-zygotic or post-zygotic
• determined by where the block is before or
  after fertilization

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Pre-Zygotic Barriers

• Temporal isolation breeding cycles are during
  different times of the year
• Eastern skunk in fall and Western in the late
  winter
• Habitat isolation live in the same region but
  in different habitats
• water vs land
• Behavioral isolation traits required to obtain
  a mate
• odor, coloration, courtship rituals
• Mechanical isolation sex organs are
  anatomically incompatible
• do not fit together to do the act of copulation
• Gamete isolation may be able to copulate but
  the embryo doesnt survive or the gametes are
  incompatible

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Courtship Dance
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Post-Zygotic Barriers

• Mechanisms that operate should you get
  interspecies mating
• forms a hybrid egg from one species and the
  sperm from another species
• Hybrid inviability offspring die before they
  reach reproductive maturity
• Hybrid sterility may become an adult but they
  will be sterile
• mule female horse and male donkey
• Hybrid breakdown F1 hybrids are viable and
  fertile but if they mate with parent or sibling
  results in feeble or sterile F2 generation
• cotton plants

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Mule
?
?
Hinny - ? horse and ? donkey
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• Usually a combination of barriers that reinforces
  boundaries keeps species separate

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Mechanisms of Speciation

• Gene pool of a population is severed from others
  populations of the parent species splinter
  group follows own evolutionary path
• 2 general scenarios
• allopatric speciation initial block to gene
  flow is a geographic barrier that physically
  separates the splinter group
• sympatric speciation new species without the
  geographic barrier becomes reproductively
  isolated right in the middle of the parent
  population

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Geologic Time and Fossil Records

• Fossils archive macroevolution produce a record
  of life on Earth in the strata of sedimentary
  rocks
• Can create a geologic time line

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• 4 comprehensive divisions
• Precambrium
• Paleozoic
• Mesozoic
• Cenozoic
• Separated by mass extinctions when many forms of
  life disappear and are replaced by diversified
  species that survived

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Aging Fossils

• Need to be able to age the fossils found
• relative age of fossils is in the order the
  fossils are found, younger on top of older
• absolute age is done by carbon dating using the
  amount of radioactive carbon to deduce age
• half-life is 5600 years so can age things that
  are less than about 50,000 years old

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Plate Tectonics

• Continents are not locked in place and the US is
  moving about 2 cm further from Europe each year
• Accounts for mountain building, volcano activity
  and earthquakes

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Continental Drift

• During Palezoic period the land masses shifted to
  one giant mass called Pangaea brought on mass
  extinction because of change in climate and
  marine water levels
• During the Mesozoic period Pangaea started to
  drift apart and again caused a mass extinction
• Following both mass extinctions (took about 10
  million years) there was an explosive
  diversification of organisms that adapted to the
  changes
• like the new and different vegetation that grows
  in the forest after a devastating fire

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Classifying Diversity

• Systematics study of diversity and
  relationships of organisms past and present
• includes the study of taxonomy
• identifying, naming and classification of
  organisms

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Basic Taxonomy

• Use the scientific name when talking about
  organisms because there are many different
  species of peas to a scientist
• common name can be misleading
• fishes can include jellyfish (cnidarian),
  crayfish (crustacean) and silverfish (insect)
• Helps ease communication among scientists

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Carolus Linnaeus

• Developed the scientific name and taxonomy in the
  1770s
• Use a binomial system with the genus and species
  in Latin
• start with capital letter and in italics
• Then add the hierarchical classification that
  gets increasingly broader until you hit the
  domain name
• YOU MUST KNOW THE ORDER
• species, genus, family, order, class, phylum,
  kingdom and domain

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Phylogeny

• Includes the history of the species and is
  depicted as a tree
• Common descendents are on the same branch
• closer they are the more related they are

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Sort Homology from Analogy

• Use homologous structures to generate the tree of
  life greater number of homologies between
  organisms the more closely related
• Some similarities are not from a common ancestor
  but are just superficially similar called an
  analogy and is formed from convergent evolution
• develop independently and from different
  structures but have a similar function like the
  wings of birds and insects

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Homology

• The more complex a structure is the less likely
  that they arose independently
• human and chimpanzee skull have similar bones and
  are assembled and fused in the same way
  indicating that they have a common ancestor

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Molecular Biology Tool of Systematics

• Comparing genes and proteins can get to the heart
  of the relatedness issue
• Evolutionary divergences of species parallel the
  accumulation of differences in the genome
• the more recent the branch they closer related
  they are
• can do DNA analysis on fossil remnants

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Cladistic Revolution

• Clades are ancestral species and all descendents
  that branch on the tree of life
• Use homologies unique to each group to generate
  the tree
• Becoming the replacement for taxonomy
• Crocodiles are more related to birds than to
  lizards and snakes as the taxonomy shows DNA
  analysis aids in these determinations

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Kingdoms in Each Domain