Evolution

• Jean-Baptiste de LaMarck- theorized about acquired traits

  • thought it happened throughout their lifespan

Darwin’s Theory

• Charles Darwin- “Descent with Modification”

  • proposed the idea of evolution by natural selection

  • said organisms descend with modification (survival of the fittest)

• Adaptive Radiation

  • populations branch out to adapt their environment

• Essence of Darwin’s Ideas

  1. Variation exists in natural population

  2. Many more offspring are born each season than can possibly survive maturity

  3. As a result, there is a struggle for existence (competition)

  4. Characteristics beneficial for competition

     • adaptions

  5. Over long periods of time, and input of variation, a new species emerges

• Wallace

  • forced Darwin to publish his book

Mechanics of microevolution

• 5 agents that act on Evolutionary change

  • mutation

    • biggest one

  • gene flow

    • Movement of individuals & alleles in & out of populations (immigration/ emigration)

    • causes genetic mixing

  • genetic drift

    • founder effect

      • When a new population is started by only a few individuals

      • happens when colonization

    • bottleneck effect

      • When large population is drastically reducedby a disaster

  • natural selection

    • Differential survival & reproduction due to changing environmental conditions

  • non-random mating

    • Sexual dimorphism

      • gender differences created by sexual selection

Evidence for Evolution

• fossils- any sign of life existed at that point

• examples:

  • 1. Tiktaalik – “missing link” from sea to land

  • 2. birds to dinosaurs

• biogeography- wallace’s line

• homology “homologous structure

• divergents- shares

• convergen- share same purpose

3structures

homzygous, anagolus

evolution of populations

• population: group of individuals of the same species in the same place at the same time

• hardy-weinberg principle

  • p²+2pq+q²=1

    • we count alleles

      • frequency of dominant alleles: f(A)=p

      • frequency of recessive alleles: f(a)=q

        • p+q=1

    • to know if a population is in hardy-weinberg equilibrium observe at least 2 generations and see if they are equal

• conditions for a population to be in hardy-weinberg (meaning not example)

origin of species

• Biological species concept- population whose members can interbreed & produce viable (healthy), fertile offspring

  • Microevolution – small changes with alleles (N.S.)

  • Macroevolution – origin of new species

• how do new species originate? Speciation

  • Populations must become isolated

  • Isolated populations evolve independently

• Isolation occurs 2 ways:

  • allopatric isolation

    • geographic separation (physical)

    • “other country”

  • sympatric isolation

    • still live in same area but don’t reproduce

    • “same country”

  How does nature maintain the species boundaries?

  • 1. Prezygotic barriers – prevents the physical act of mating or fertilization by sperm cell

    • examples:

      • geographical isolation- species occur in different places

      • (habitat isolation) sympatric speciation- Species occur in same region, but occupy different

        habitats so rarely encounter each other

      • temporal isolation- breed during different seasons

      • behavioral isolation- Unique behavioral patterns & rituals isolate species

      • Mechanical Isolation (sympatric)- Morphological differences can prevent successful mating

  • 2. Postzygotic barriers – barriers that form after hybrid zygote is formed

    • reduced hybrid viability- poor health

    • reduced hybrid fertility- sterile

• speciation rate

  • gradualism- gradual accumulation of small changes over time

  • punctuated equilibrium- rapid burst of change mixed with long periods of little to no change

Classification, phylogeny and the tree of life

• systematics- the discipline of biology that focuses on classifying organisms and determining their evolutionary relationships

• taxonomy

  • binomial species- each species has two part name

    • genus and species

• classification

  • domain

    • kingdom

      • phylum

        • order

          • family

            • genus

              • species

• old 5 kingdom system

  • monera (prokaryotes), protists, plants, fungi, animals

• new 3 domain system

  • prokaryote: bacteria

  • prokaryote:archaebacteria

  • eukaryotes

    • protists, plants, fungi, & animals

phylogeny

• phylogeny- evolutionary history of species or group of species

  • phylogenies based on homologies reflect Evolutionary history (divergent evolution)

  • know how to read a phylogenetic tree (cladogram)

origin of life

• origin of life is a hypothesis

  • special creation: where life was created by an otherworldy force (non testable)

  • extraterrestrial origin (panspermia): orginal source of organic materials comes form comets (testable)

  • abiogenesis: life evolve spontaneously from inorganic molecules (testable)

• conditions on early earth

  • reducing atmosphere- lots of different gases, available H atoms, no free oxygen

• 1953 miller and urey test hypothesis- closed system that produced amino acids, hydrocarbons, nitrogen bases, ETC.

• endosymbiotic theory- how did life get here

  • prokaryotic ancestor of eukaryotic cells, eukaryotic cells

  • eukaryotic cell: origin of mitochondria

• macroevolution patterns

  • adaptive radiation – species migrate to new environment

  • convergent evolution – adaptations due to similar environment

  NOT evolutionary relationships

  • Macroevolution – the quick,abrupt change to many

  populations that happens

  suddenly.