Bio 106 first test

Ideas before darwin:



Special Creationism 

  • Fixity of Species: Species are created by god for specific habitats and don’t change

  • Fixity of Earth: Earth’s age is 6k yrs and landscapes don’t change

- Scala Naturae(Aristotle): 

  • Species are fixed and there is a hierarchy of complexity in species (linear hierarchy).

-Linneaus:

  • Species could be clustered into nested categories 

-Jean Baptiste de Lamarck

  • fSpecies can change over time

  • Traits can be inherited

  • Traits change based on use and disuse

-Charles Lyell

  • Geologist–earth is old

  • Earth gradually changes over time



Darwin’s Journey

  • Sailed on HMS Beagle as a Naturalist

  • At fist believed special creationism, but doesn’t match up with observations

    • Found fossil sea shells at 10k ft in the andes and then saw earthquake that uplifted living mussels 10 ft–earth can’t be 6k years old cause lyell

    • Found endemic species on Galapagos Islands

      • Unique species, but still shared features

      • Since islands are geologically new, so he thought species migrated b/c many birds and reptiles that could theoretically migrate. HOWEVER, endemic species.

THEORY OF EVOLUTION

  • Descent with Modification

    • Populations accumulate modifications generation to generation

    • Small changes become big changes

    • Populations become much more different than their ancestors

    • Species are related to each other by shared lineages(phylogenetic branches)

  • On the Origin of Species

Natural selection

Components:

  1. Genetic variation 

  2. Selective pressure (selects some variants over others)

  3. Reproduction (favorable traits passed to offspring)



Selective pressure:

-individuals experience struggle for existence leading to different reproductive success

-Competition for resources—populations usually produce more offspring than the environment can support, so individuals with better traits will survive and reproduce more. 



Ex. pepper moths, cotton bollworm



Selective pressure: insecticides



Variation: some bollworms were more resistant to the insecticides.



Nex generation more resistant to the insecticides.



Linnean system of Classification

Taxonomy-naming and classifying living organism

  • Linneaus developed the binomial classification system in 18th century

Binomial nomenclature: genus + specific epithet

  • Name is always italicized

  • Genus is always capitalized

  • Specific epithet is never capitalized

  • Can shorten by using initial for genus: P. concolor

Categories:

Species

Genus

Family

Order

Class

Phylum

Kingdom

Domain

Phylogenetic Trees

  • Relationships depicted as a series of dichotomies

  • Nodes is the common ancestor that experiences reproductive isolationn

  • Gene flow became split as gene flow between subpopulations became restricted 

What it shows:

  • X-axis is time (oldest to most recent) Trunk to branches

How to use traits to determine relatedness

  • Traits can be physical or DNA(genes)

  • DNA is most reliable for identifying evolutionary relationships

  • Useful traits are genetically based–inherited from a common ancestor

    • Useful shared traits are Homologous traits, they are inherited

    • Not useful similar traits are Analogous. They aren’t inherited from a common ancestor, but instead due to living in similar environments. 

      • Results from convergent evolution

  • In phylogeny, traits are called characters

    • Different options are called character states

    • Ancestral states are at the root of the tree (bottom of the tree)

  • Branches can rotate around a node without changing the relationships

Classification:

  • Monophyletic: All of the descendants of a single ancestor plus the common ancestor itself. (AKA Clade)

  • Paraphyletic group: Some of the descendants of a single ancestor plus the common ancestor 

  • Polyphyletic group: Unrelated descendants without a single ancestor. 



Cell division

Chromosome terms:

  • Diploid: Two sets of chromosomes

  • Haploid: One set of chromosomes



Mitosis: cell division that makes cells identical to the original cell

Meiosis: cell division that takes a diploid cell and makes haploid daughter cells



Plantae

Plants and algae shared characteristics

  • Multicellular, eukaryotic

  • Cell walls of cellulose (some algae)

  • Special organelles: chloroplasts for photosynthesis, making them autotrophs

Defining traits of plants

  • Alternation of generations in life cycle: sporophyte–gametophyte generation

    • Walled spores produced in sporangia

  • Apical meristems: growth buds at the anterior end of the shoot

Alternation of Generations:

Diploid Sporophytes:

  • Multicellular w/diploid (2n) cells

  • Reproduce by creating haploid spores inside an organ through meiosis(sporangium)

  • Spores grow up into gametophytes

Haploid Gametophytes

  • Multicelluar w/ haploid (1n) cells

  • Reproduce by creating haploid sperm and eggs (gametes) inside sex organs

  • Sperm and eggs fuse into diploid zygote

  • Zygote grows up into the Sporophyte






Land plants

Reasons for moving to land:

  • Unfiltered  light

  • More CO2

  • Nutrient rich soil

  • No competitors

  • No predators

Challenges:

  • Desiccation( drying out )

    • Body

    • Gametes

    • embryos

  • Structural support against gravity

  • UV exposure



Non-Vascular Plants

Mosses, Liverworts, Hornworts

  • Gametophyte stage is dominant

  • Low-lying plants b/c no vascular system

  • Form dense carpet of leaves

  • Grow on moist surfaces (rocks, logs, trees)

    • Flagellated sperm need water to swim and fertilize egg

  • Lack of roots–rhizoids anchor plant

    • Little absorpitive function

    • All water + nutrient absorption happens through leaves 

      • Higher surface area to volume ratio

Moss lifecycle

  • Gametophyte: dominate stage(leafy rug)

  • Sporophyte stage (stalk that lives on gametophyte body)

Seedless Vascular plants

Lycophytes and Monilophytes

  • Have vascular tissue

  • Allows plants to grow taller

  • First to have developed roots and leaves

  • Still needs moist environments for reproduction

    • Sperm still needs to swim to egg

  • No seeds or flowers

  • Sporophyte is the dominant form


  • Sorus: cluster of sporangia



Vascular Tissue

  • Xylem: transports water and minerals

  • Phloem: transports sugar(glucose) from leaves to other tissue



Advantages: 

  • Allows taller growth

  • Outcompetes for sunlight(more photosynthesis)

  • Can disperse spores from higher, more widespread dispersal



Roots: 

  • anchor plants in ground

  • Absorb water and soil nutrients

  • Use vascular tissue to distribute them upward(xylem)

Leaves:

  • Photosynthetic organ (stomata)

  • Captures CO2 from air

Seed plants: Gymnosperms & Angiosperms

Adapted to counter desiccation:

  • Protected gametophyte: sporophyte dominates life cycle, retains gametophyte within sporophyte

  • Protected sperm: Pollen 

  • Protected embryos: Seeds



Gametophytes are separate sexes (male & female)

  • Pollen is male gametophyte

    • Makes sperm inside antheridium

  • Ovule is female gametophyte

    • Makes eggs inside archegonium



Seeds are containers for the embryos

  • Contains nutrients to feed embryo



Gametophyte is retained in Sporophyte

  • Protects gametes

  • Gymnosperms: gametophytes develop and live inside male and female cones

  • Angiosperms: develops and live inside the anther (male flower) and ovule (female flower)

Seed Plant reproduction


Female sporophyte: makes megaspores

Male sporophyte: makes microspores



Gymnosperms:

  • Includes 4 living plant groups: Cycads(130 species), Gingkos(1 species), Gnetophytes(30 species), conifers(600 species)

  • sporangium is inside the cone

  • Male cones create microspores from microsporangia

  • Female cones create megaspores from megasporangia

  • Female gametophyte is tiny and is retained inside the sporophyte body(cone)

  • Male gametophyte (pollen) : male cones house microsporangia that make microspores, which develop into pollen (gametophytes).

    • Pollen is shed from cone

    • Lucky ones land on female gametophytes



Seed formation 

  • Female Gametophyte produces egg

  • When egg is fertilized, zygote grows into embryo

  • Ovule retains it and becomes the seed

  • Integument becomes seed coat

  • Food supply comes from female gametophyte tissue



Angiosperms

Shares key features w/ gymnosperms:

  • Sporophyte is dominant

  • Female gametophyte retained in sporophyte body

  • Gametophytes are pollen and ovules

  • Creat seeds ot protect embryos



Differences:

  • Spores are in flowers

  • Seeds are in fruit

Flowers & Fruits

Flowers: sex organs (antheridium and archegonium)

  • Spore factory which grow into gametophytes

  • Attract pollinators that carry pollen from flower to flower

Fruit

  • Aids seed dispersal to new locations