Biology 150

Biology 150

1. Biodiversity

   • Is the variety of life on Earth in all its forms and interactions
   • Consequences of decline
     • Once an animal goes extinct, there's no bringing it back
     • Plants could've been used to cure diseases, but once extinct it's over
     • Essentially "burning the library of life"
     • Planetary Boundaries
       • Essentially inform how much can the planet withstand climate chance, chemical pollution, etc. They explain the effects of this and how much we can withstand before it is too late.   
       • There are 9
     • Less Speciation
   • Evolution
     • Evolution is a change in the frequency of alleles or genotypes in a population over time.
     • Genetic Variation
       • Genetic variation refers to differences in DNA sequences.- When a mutation occurs in a gene, it creates a new allele.- Mutations can be deleterious, neutral, or advantageous.
     • Genetic Drift
     • Phylogenetic tree
       • Is a hypothesis of the evolutionary relationships among organisms
       • Nodes , branching point
         • Sister groups = more closely related
       • Groups:
         • Monophyletic group
           • includes all descendants of a common ancestor 
         • Paraphyletic group
           • includes some, but not all of the descendants of a common ancestor 
         • Polyphyletic group
           • includes organisms from distinct groups based on shared convergent characters, does not include a common ancestor 
       • Homologous and analogous
         • Synapomorphy implies that homologous trait is from same ancestor
       • Molecular data provide best information (uses DNA sequences)
     • We can track it with fossil records
       • Carbon 14 for fossils 50,000 years or less
       • Uranium and Lead for longer
       • Permian period= largest mass extinction

2. Natural Selection

   • Finches in Galapagos
     • Deep beaks can break hard seeds
     • Short beaks can easily break soft seeds
     • Drought has 84% mortality among finches
       • Finches with deep beaks survive
         • Next generation of finches has deeper beaks, example of natural selection.
     • Hardy Weinberg Theory
       • This theory further illustrates could show if there was any evolution in these species after the drought!
       • 5 assumptions
         • the population experiences no selection, no migration, no mutation, no sampling error due to small population size, and random mating. 
     • Sympatric, finches lived in same geographic location, but had large vs small beaks
       • sympatric means populations that are in the same geographic location. 
     • Speciation
       • Speciation is typically a by-product of genetic divergence that occurs as a result of the fixation of different mutations in two populations that are not regularly exchanging genes.
       • Genetic divergence between the small and large beak finches
       • If divergence lasts long, it will result in reproductive barriers between populations
         • Most speciation is allopatric
           • involving two geographically separated populations
         • Geographic separation can be caused by dispersal or vicariance
           • dispersal, resulting in the establishment of a new and distant population, or by vicariance, in which the range of a species is split by a change in the environment
   • Process where organisms better adapted to the environment tend to survive and have more offspring
   • Genetic Drift
   • Intra and Intercellular selection
     • - In intrasexual selection, individuals of the same sex compete with one another, resulting in traits such as large size and horns. - In intersexual selection, interactions between females and males result in traits such as elaborate plumage in male birds.  

3. BSC

   • The biological species concept (BSC) states that species are groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups. 
   • Doesn't apply to asexual or extinct organisms

4. Reproductive Isolation

   • Reproductive isolation is caused by barriers to reproduction before or after egg fertilization.
   • Pre Zygiotic, before egg fertilization
     • temporal
     • behavioral
     • Gamete barrier
     • habitat
     • mechanical
   • Post zygotic, after egg fertilization
     • Mating occurs, but genetic incompatibilities prevent viable offspring. Such as chromosomal difference

5. the 3 domains of life

   • Bacteria
     • are small and lack a membrane organelle, no nucleus, cell wall, and diffusion limits their size. Genome is circular 
     • cell wall made of peptidoglycan
     • Bacteria are small and lack membrane-bounded organelles
       • The bacterial genome is circular. Some bacteria also carry smaller circles of DNA called plasmids.
         • obtain DNA by horizontal gene transfer from organisms that may be distantly related
     • Diffusion limits size in bacterial cells.
   • Archaea
     • Some of them are extremophiles, meaning they can withstand extreme temperatures, others live in salty areas. 
     • Prokaryote earliest life form
       • no nucleus 
     • No peptidogylcan in cell wall
     • Some archaeons are extremophiles
       • They live in extreme environments 
   • Eukaryote
     • Includes animals, fungi, plants, and protists, but then divided into 7 superkingdoms
       • There are 7 superkingdoms in Eukaryotes
         • stramenopiles, alveolates, and rhizarians dominate eukaryotic diversity in the oceans
       • Most eukaryotic cells have mitochondria, but a few do not. Evidence suggests that cells lacking mitochondria once had them but subsequently lost them.
         • The endosymbiotic hypothesis proposes that the chloroplasts and mitochondria of eukaryotic cells were originally free-living bacteria.
       • Protists are eukaryotes that do not have features of animals, plants, and fungi; algae are photosynthetic protists; and protozoa are heterotrophic protists.
         • Protista consists of heterotrophic and autotrophic organisms whereas most protozoa are heterotrophs.
     • Have a nucleus, this makes them distinct from prokaryotes
     • Sexual reproduction , promotes genetic diversity
     • Larger genomes than prokaryotes
   • Many obtain energy from fermentation
     • Sulfur & Nitrogen cycles

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