Exam 1 & 2 Review Notes

Convergent Evolution

  • Definition: When different evolutionary lineages develop similar traits and/or ecological niches due to similar selective pressures.
  • Key Point: SIMILAR selective pressures cause organisms from DIFFERENT lineages to adapt to SIMILAR traits.

Artificial Selection

  • Definition: Human-induced selective pressures that accentuate desired traits in organisms like livestock, pets, or plants.
  • Process: Selecting specific individuals to breed based on desired traits, leading to evolution and domestication.
  • Examples of Traits: Behavior, coat color, cartilage, hormones, reproductive cycling.

Evolution at the Population Level

  • Individual organisms do not evolve; POPULATIONS evolve.

Evolutionary Change

  • Definition: Heritable change in one or more characteristics of a population/species from one generation to the next.

Necessary Conditions for Evolution via Natural Selection

  • Variation of Traits: There must be variation in traits within a population.
  • Differential Reproduction: Variation must affect fitness, with individuals having "best" traits producing the most offspring.
  • Heritability: Traits must be heritable.
  • Natural selection can only increase or decrease heritable traits that vary in a population

Horizontal Gene Transfer

  • Definition: The exchange of genetic material between organisms, but not between parents and offspring.

Homologous Structures and Genes

  • Homologous Structure: Fundamental similarity due to descent from a common ancestor.
    • Examples: anatomical, developmental, molecular/genetic (DNA).
  • Homologous Gene: Same formation, different function.
    • Broad skeletal similarity due to a common ancestor

Gene Pool

  • Definition: The total array of alleles in a POPULATION.

Frequency-Dependent Selection

  • Negative Frequency-Dependent Selection:
    • Less common traits have higher fitness.
    • Leads to balancing selection.
  • Positive Frequency-Dependent Selection:
    • More common traits have higher fitness.
    • Does not lead to balance.

Evolutionary Response to Ivory Poaching

  • Example: Evolution of tusklessness in some elephant populations as a response to intense ivory poaching.

Hardy-Weinberg Equilibrium

  • Variables:
    • pp: represents the frequency of the dominant allele.
    • qq: represents the frequency of the recessive allele.
  • Genotype Frequencies:
    • p2p^2: represents the frequency of homozygous dominant individuals.
    • q2q^2: represents the frequency of homozygous recessive individuals.
    • 2pq2pq: represents the frequency of heterozygous individuals.

Hardy-Weinberg Equilibrium Conditions

  • Conditions:
    • No mutations.
    • Random mating.
    • No natural selection.
    • Large population size.
    • No gene flow.

Biological Species Concept

  • Definition: A group of INTERBREEDING natural populations that are REPRODUCTIVELY ISOLATED from other such groups.

Macroevolutionary Change

  • Definition: Formation of new species or groups of species.
    • Large scale changes visible in the Tree of Life.

Adaptive Radiation

  • Definition: Evolution of new forms from a single ancestor to exploit new ecological opportunities.
  • Examples: Darwin’s finches, honeycreepers, fruit flies.

Genetic Drift

  • Definition: A RANDOM change in allele frequencies over generations.
    • Caused by random sampling.
    • Examples: Death by chance, not connected to genetics/fitness.
    • Larger impact on smaller populations.

Bottleneck Effect

  • Definition: REDUCTION in genetic diversity due to only a subset of individuals surviving.
    • Example: Impact of geographical/natural disasters.
    • Future generations have genotypes + phenotypes of survivors.

Reproductive Isolation

  • Prezygotic Isolation: Prevents interbreeding between populations before fertilization.
    • Gametic isolation: different courtship + rituals
    • Mechanic isolation: physical differences preventing reproduction
    • Temporal isolation: (time) different reproductive cycles, gamete release does not cross
  • Postzygotic Isolation: Occurs after mating/fertilization.
    • Hybrid inviability: the zygote will not survive.
    • Hybrid sterility: offspring cannot reproduce (i.e., mules (horse + donkey)).
    • Hybrid breakdown: over successive generations, offspring become weaker or sterile.

Temporal Isolation

  • Definition : (time) different reproductive cycles, gamete release does not cross

Speciation

  • Allopatric Speciation: 2 species are geographically separated, leading to reproductive isolation.
  • Sympatric Speciation: 2 populations are overlapping but become reproductively isolated.
    • Examples: change in beak shape, song production change → reproductive isolation

Heterochrony

  • Definition: Change in timing or rate of developmental events.
    • cats/kittens (similar skull shape)
    • Vs
    • dogs/puppies (different skull shape → changes from puppyhood to adulthood)

Principle of Parsimony

  • Definition: The simplest explanation for a phenomenon; the phylogeny tree with the fewest evolutionary changes.

Pax6 Gene

  • Function: Evolution/development of eyes during embryonic development.

Taxonomic Levels of Organization

  • Order:
    • Domain
    • Kingdom
    • Phylum
    • Class
    • Order
    • Family
    • Genus
    • Species

Binomial Nomenclature

  • Definition: 2-part naming system.
    • Genus species.

Phylogenetic Groups

  • Monophyletic Group/Clade:
  • Paraphyletic Group
  • Polyphyletic Groups

Haploid and Diploid

  • Haploid (n): contains 1 set of chromosomes.
  • Diploid (2n): contains 2 sets of chromosomes.

Polyploidy

  • Definition: an organism’s cells contains MORE than 2 complete sets of chromosomes

Hox Genes

  • Definition: Homeotic gene complexes.
    • Important for body plan (especially anterior/posterior).

Proximate vs. Ultimate Questions

  • Proximate: HOW diversity is generated.
  • Ultimate: WHY diversity is maintained.

Genotype and Phenotype

  • Genotype: DNA/genetics that code for a trait; determines phenotype.
  • Phenotype: influenced by genotype, physical traits.

Shared Traits

  • Shared Derived Trait: evolutionary novelty unique to a particular clade.
  • Shared Ancestral Trait: trait that originated in a ancestor of the taxon

Protist Groups

  • Amebozoa:
    • Moves and ingests food with pseudopods.
  • Choanoflagellates:
    • Most closely related to animals. Feature distinctive collar surrounding flagella → “modern protists”
    • Most related to common ancestor of animals
    • Can form sponges
  • Stramenopila:
    • Have strawlike hairs on their flagella
    • Wide range of algae, protozoa, + fungus-like protists
    • Named for straw-like hairs on surface of flagella
    • heterotrophic/photosynthetic
    • ie. Diatoms
  • Alveolata:
    • Protists with saclike membranes on the outside of their cell
    • Saclike membranous vesicles (alveoli) present in cell periphery
    • Dinoflagellates → some photosynthetic
    • Apicomplexa
      • Medically important parasites
      • Apical complex
      • Plasmodium
    • Dinozoa
      • Red tie + mutualistic relationship with coral (polyps)
  • Rhizaria:
    • Protists that exhibit thin, hairlike extensions of cytoplasm radiating out from itself
    • Have thin, hair-like extensions of the cytoplasm → filose pseudopodia (thread-like hairs)
    • Phylum Radiolaria
    • Phylum Foraminifera
    • Animal-like

Malaria-Causing Protist

  • Plasmodium.

Protist Characteristics

  • Not all protists are unicellular but MOST are
  • ALL PROTISTS are EUKARYOTIC.
  • They do not share the same nutritive mode.

Cambrian Explosion Hypotheses

  • 1) New predatory-prey relationship (selection)
  • 2) A rise in atmospheric oxygen (resources)
  • 3) Evolution of Hox gene complex + addition of new microRNA → involved in a gene regulation

Endosymbiosis

  • Definition: a symbiotic relationship in which an organism lives inside another
  • Evidence: mitochondria + chloroplasts
    • Have own DNA
    • DNA circular shape → matching prokaryotes
    • Gram-postitive: shows violet stain →indicates presence of peptidoglycan (aka cell wall)
    • Gram- negative: stays red → indicates no peptidoglycan (aka no cell wall)
    • Replicate like prokaryotes → binary fission + separate from rest of cell
  • Secondary Endosymbiosis: a eukaryotic cell engulfs a cell that has ALREADY undergone primary endosymbyosis → > 2 membranes

Flagellum

  • Definition: Hair-like appendage used by some protists to swim.

Protozoa

  • Definition: Animal-like protists that are heterotrophic (no evolutionary meaning).

Protist Classification

  • Classified in the past by: ecological role + habitat + motility, but they have no evolutionary meaning → therefore, they are NOT MONOPHYLETIC

Cleavage

  • Determinate cleavage: fate of cells determined early.
    • Protosomes
  • Indeterminate cleavge: each cell retains capacity to generate embryo
    • Most bilateral
    • Deuterstomes

Coelom

  • Definition: true body cavity
  • Derived from mesoderm → located between external body eall and digestive tube
  • MESODERM
  • Coelomate: posses true coelom/tissue lining coelom + suspending internal organs

Acoelomate and Pseudocoelomate

  • Acoelomate: tissue-filled region
  • Pseudocoelomate: muscle layer

Photosynthesis

  • Definition: a type of autotroph; organism that carries out photosynthesis by means of food and production

Prokaryote Capsule

  • Definition: sticky outer layer (some)
    • Allows for adherence to substrate/each other
    • Symbiotes + pathogens

Bacterial Toxins

  • Endotoxins: (lipopolysaccharids) found in the OUTER membrane of GRAM-NEGATIVE bacteria
  • Ectotoxins: (proteins) secreted by BOTH gram-negative and gram-postiive bacteria

Bacterial Shapes

  • Spherical: cocci
  • Rod: bacilli
  • Spiral: spirilla

Heterocyst

  • Definition: Nitrogen-fixing cell → contained in cyanobacteria

Gene Transfer in Prokaryotes

  • Transduction: genes moved by phages (viruses that infect bateria)
  • Transformation: foreign DNA from environment
  • Conjugation: transfer between bacteria (pilus)

Prokaryotic Reproduction

  • Mostly reproduce via BINARY FISSION (ASEXUAL)
    • Less variation, more efficient, ability to adapt quickly
  • Sexual reproduction allows for more variation → combination of parent genomes

Aerobic and Anaerobic

  • Obligate arobe: reiquire O2O_2
  • Obligate anarobes: poisoned by O<em>2O<em>2 + lives by fermentation/use substances other than O</em>2O</em>2 for anaerobic respiration
  • Faculative anaerobe: can use O2O_2/carry out fermentaton/anaerobic respiration

Bioremediation

  • Definition: Natural process using microorganisms (ie. bacteria) to clean up contaminated soil/water/other environments
    • Use of microorganisms to remove pollutants from the environment (ie. oil spills)

Utility and Benefits of Prokaryotes

  • Chemical recycling → decomposeres: break down dead organisms + waste products
  • Mutualism (symbiosis)
  • CRISPR-Cas 9 system that can alter genes in other organisms
  • Can be used to make natural plastics
  • Bioremedation

SSU rRNAs

  • Small subuinit of ribosomal RNAs
  • Universal in all organisms
  • Slow mutation rate

Key Features of Animals

  • Consumers/heterotrophs
  • Multicellular eukaryotes
  • Cell + tissue specialization
  • Developmental similarities?

Nutritive Mode of Animals

  • Heterotrophy

Obstacles to Evolving Multicellularity

  • Requires cooperation of cells (only some reproduce)
  • Volvox used to study evolution of multicellularity
  • Aggregation
  • Central control
  • Communcation
  • Division of Labor

Cyst

  • Definition: Protective walls; dormant
    • Portozoan pathogens/parasites spread from one host to another via cysts
    • The dormant part of the parasite’s life cycle, protective stage that allows the parasite to survive outside the host/environmental conditions
    • Infectious form, responsible for transmission to new hosts

Sister Taxa to All Other Animals

  • Porifera (sponges) are the most closely related group of animals to all other animal groups

Myxozoans

  • CNIDARIA → myxozoa
    • Highly derived cnidarian relatives
    • Obligate parasites
    • Extremely small genomes (some lack mitochondria)
    • Reproduce via spores

Animal Group with Medusa Stage

  • CNIDARIA → medusa

Animal Group Lacking Tissues

  • PORIFERA (sponges) → lack true tissues
    • Basal (out) group

Collar Cells in Sponges

  • Collar cells → choanocytes: play a role in feeding, respiration, and reproduction
    • Whip-like tail/flagellum + collar of microvilli
    • Tail creates currents drawing water into the sponge (bring in oxygen and food) + collar traps food particles
    • Some collar cells can also transform into sperm cells for reproduction

Protostome vs. Deuterostome Development

  • Differ in cleavage, coelom formation, fate of the blastopore
  • Protosomes: determine fate of cells early in development
    • Spiral (and determinate) cleavage
    • Blastospore develops into the mouth
    • ie. molluscs, annelids, arthropods
  • Deuterostomes: indeterminate fate of cells
    • Most bilateral
    • Radial (and indeterminate)-cleavage
    • Blastospore develops into the anus
    • ie. echnioderms, chordates

Triploblast vs. Diploblast

  • Diploblast: develop from 2 germ layers (ectoderm + endoderm)
    • Simpler body plans
    • Jellyfish
    • Ctenophores? → presence of muscle cells creates ongoing debate of whether they are di/triploblatic → still only a presence of 2 germ layers
  • Triploblastic: develop from 3 germ layers (ectoderm + endoderm + mesoderm (between ecto/endoderm layers)
    • All bilaterally symmetric
    • Mesoderm allows for development of more complex tissues/organs/organ systems → greater diversity of body plans/behavior

Grade in Evolutionary Biology

  • Grade: organisms that have similar body plan or key biological features
    • Not necessarily clades or monophyletic groups
    • ie. germ layers/coelomates/true tissues.
    • Useful in differentiating animals, but are graded

Arthropods

  • Key Identifying Features: segmented body/hard exoskeleton/jointed appendages
    • Early arthropods→ less segmentation → less variation
    • Tagmata = segments fused into functional units
    • Specialization not driven by novel hox genes, but more likely by changes in sequence/regulation of existing hox genes
    • Nearly all biospheres/habitats
    • One of first animals to colonize land
    • Open circulatory system → gas exchange specializations → internal gills (water) + trachea (land) +spiracles that draw in air

Arthropod Subphyla

  • Subphylum Chelicerata: 6 pairs of appendages
    • Class merostomata (horseshoe crabs)
    • Class arachnida (spiders)
      • Book lungs + trachea
  • Subphylum Myriapoda (centipedes + millipedes)
    • Centipede→ carnivore → one leg/segment → increases speed
    • Millipede → decaying matter
  • Subphylum Crustacea/ Pancrustaceans
    • Class Malacostraca (crayfish)
      • Crabs, lobsters, shrimp, barnacles, land isopods
      • Marine/freshwater/terrestrial habitats
      • Smaller: exchange gases through cuticle
      • Larger: have gills
      • Highly specialized appendages

Metamorphosis

  • Complete metamorphosis: egg → larva → pupa → adult
  • Incomplete metamorphosis: egg → nymph → adult

Lophophore

  • Definition: Horse-shoe shaped crown of ciliated tentacles.
    *Aids in feeding, creates water current that draws in food particles

Acoelomate Protostomes

  • Platyhelminthes → triploblastic acoelomates

Invertebrate Classification (Examples)

  • Spiny-headed Worms: Acanthocephalans (highly modified rotifers, sexual reproduction)
  • Crustaceans: (various species mentioned)
  • Snails: gastropods (Mollusca)
  • Octopuses: cephalopods (Mollusca)
  • Annelids:
    • Sedentaria: earthworms, leeches (more sedentary, burrowers)
    • Errantaria: marine predators (more mobile)

Key Anatomical Features

  • Tracheae and book lungs
  • Dorsal: Back
  • Ventral: Belly
  • Anterior: Head
  • Posterior: Tail
  • Tagmata = segments fused into functional units
  • Segmentation: serially repeated body structures

Mutualism

Most Intelligent Invertebrate

  • Octopus (Mollusca → cephalopoda)

Plant Groups

  • Vasculature
  • Seeds: Gymnosperms
  • Flowers: Angiosperms

Evolution of Flowers

  • Non-vascular plants (bryophytes):
    • No true tissues
    • Reproduce via spores (n)→ asexual reproduction
    • Restricted in size (cannot draw water up) → require moist environment
    • Gametophyte dominant (aka haploid dominant)
  • Seedless, vascular plants:
    • Have true leaves/stems/roots
    • leaf/sporangia on leaves (2n)
    • Spores inside sporangium/gametophyte (n)
    • Sporophyte dominant (aka diploid dominant)
  • Gymnosperms:
    • Have seeds → specific to gymnosperms
    • Exposed or on scales of cones
    • Embryonic sporophyte (2n) provides young plant abundant food supply + protection (ie seed coat)
    • Heterosporous → produce both male and female spores
    • Male cones produce pollen
    • Sporophyte dominant (aka diploid dominant)
    • Gametophyte dependent on sporophyte (specific to gymnosperms but can also apply to angiosperms)
  • Angiosperms:
    • Vasculature, seeds, flowers, and fruits
    • Pollination
    • Seed dispersal specialization:
      • Wings
      • Seeds within berries
      • Barbs
      • Utilizing wind/water for mobility
    • Diploid dominant

Fungi

  • Cordyceps fungus interesting (also includes Ophiocordyceps genus)
  • Contrast septate and coenocytic fungi

Gemma cup

  • Definition: What is a gemma cup? What is its function?

Closely Related Organisms

  • Protists most closely related to fungi, plants, animals

Monocots and Dicots

  • Features to differentiate monocots and dicots

Plant Terminology

  • Dioecious
  • Strobilus
  • Apical meristem
  • Xylem
  • Phloem
  • Double fertilization
  • Pollen
  • Ovule
  • Arbuscules
  • Zygosporangium
  • Basidia
  • Karyogamy
  • Plasmogamy
  • Conidia

Fungi

  • Generalized life cycle of fungi
  • How fungi get their nutrition?

Pollination

  • Compare the efficiency of pollination by wind and by pollinator

Sym genes in plants

  • What is the relevance of the sym genes in plants

Relationships

  • Of plants, animals, and fungi, which are most closely related to each other? How can we know?
  • Use the diagram to answer questions about plant life cycles