Exam #3 - Zoology

Lecture 9: Micro and Macroevolution

Microevolution - changes in allelic frequency in a population over time


Macroevolution - large scale evolutionary events such as speciation or extinction

→ time for cumulative small changes is important for this


Sources of genetic variation:

  • mutation - caused by errors in replication, UV radiation, chemical exposure

  • crossing-over

  • independent assortment

  • segregation

  • gene flow


Gene pool - all the alleles in present in population

→ any gene with one allele is fixed


Population - group of individuals in the same area and of the same species that interbreed


Alleles - one of two or more versions of DNA sequence (a single base or a segment of bases) at a given genomic location

  • different forms of a gene


Hardy-Weinberg equilibrium conditions:

  • populations not changing allele frequencies across generations

  • assumes that mating is random

  • things that lead to no change:

    • no mutations

    • random mating

    • no natural selection

    • extremely large population size

    • no gene flow


Limitations of natural selection:

  1. non-perfect fits

    Ex: bunny coat colors that stick out in different regions (brown bunny in snow)

  2. variation limitation - natural selection only acts on existing variance

  3. evolution is built on existing ancestral structures

  4. chance and environment - random events having big impacts


Speciation - process by which one species splits into two

Ex: ancestor finch → natural selection → beak for insects, beak for seed eating, beak for woodpecker type insect eating


Interspecies variation:

  • morphs

  • breeds

  • subspecies/race


Linnaean hierarchy - system for classification based on similarity


Sister taxa - two groups share a common ancestor not shared by an y other group

Lecture: protists et al.

4 Eukaryotic groups:

  1. excavata

  2. SAR

  3. archaeplastida - reg/green algae

  4. unikonta - fungi


Eukaryote v. prokaryote:

  • eukaryotes are everything but bacteria

  • prokaryotes have no nucleus or membrane bound organelles


Protists:

  • unicellular, simple eukaryotic organisms that are neither plants nor animals or fungi

  • not a monophyletic group


Algae v. amoeba:

  • algae - aquatic plant-like organism, everything that does photosynthesizes

  • amoeba - blob, not a consistent shape, not monophyletic

    • have pseudopods

    • false feet


Two protist caused diseases:

  1. malaria - single cell protist that loses functionality of the red blood cells when infected

  2. dinoflagellates - releases toxins that kill fish may pose human danger


3 protist feeding strategies:

  1. makes their own food

  2. gathers food

  3. can do both

Ex: filter feeding - bringing small particles into their cells


Choanoflagellates:

  • sister to animals - closest living single celled relative of all animals

    • MAIN REASON: because choanoflagellate is similar cell to a sponge

  • function and structure:

    • use collar of microvilli to filter feed


3 types of symmetry and example of a group that has each one:

  1. bilateral symmetry - one way only

  2. radial symmetry - starfish

  3. no symmetry - sponges

Ex: humans

Lecture: Porifera and Cnidaria

Sponge anatomy & ecology:

  • lack anatomy

  • filters food particles and create current

  • similar to single cellular choanoflagellates


Cnidarian anatomy & ecology:

  • ectoderm and endoderm

    • no mesoderm

  • nerve net with sensory organs

  • tentacles surrounds mouth/anus

  • force prey into gastrovascular cavity and secrete enzymes


Two cnidarian morphs & distributed across a life cycle:

  1. medusa - jellyfish-like, sexually

  2. polyp - asexually

→ medusa makes eggs and sperm, grows into larva, sticks to something and becomes a poly, makes baby jelly asexually, grow into adult


Paedomorphic life cycle - skips and looks like an ancestral kid


Cnidocytes:

  • unique cell type in cnidarians

  • contains cnidocysts

    • organelles that expel a needle-like thread to puncture prey

  • spring- loaded


Medusozoans v. Anthozoans:

  • medusozoan - produce medusa or jellyfish

    • alternates between polyps and medusa across ontogeny

  • anthozoan -

    • most are colonial

    • some filter feed

    • the anemones and corals

    • no medusa stage

    • are paedomorphic


Lecture: Platyhelminthes and Rotifers

Major features of Bilaterians:

  • 3 germ layers

  • bilateral symmetry

  • body cavity


Major groups in the clade Lophotrochozoa:

  • platyhelminthes

  • rotifera

  • acanthocephala


Free-living (planarians) v. parasitic (tapeworms/trematodes) platyhelminths:

  • Free-living -

    • not parasites

    • predators and scavengers

    • eats dead things

    • known as planarians

  • parasitic -

    • more than half of species

    • complex life cycles with multiple hosts

    • tapeworms are mostly vertebrae

      • no mouth

      • no gut


Describe a rotifer:

  • still multicellular and have specialized organs

  • reproduce sexually but depends on environment conditions

  • virgin birth strategy


Lecture: Mollusca

Bivalvia:

  • mantle - lines both shells

  • foot - use to move or swim

    • looks like a tongue to latch onto things

  • radula - NONE

  • shell - two hinged valves

  • mass - between shells


Cephalopoda:

  • mantle - forms siphon

  • foot - tentacles and siphon that glide

  • radula - present

  • shell - reduced to a pen in squid, present in nautili

  • mass - centralized


Gastropoda:

  • mantle - secretes spiral shell

  • foot - ciliated food to glide along mucus trail

    • on belly

  • radula - present

  • shell - spiral in shells

  • mass - twisted from torsion


Polyplacophora:

  • mantle - surrounds body under 8 dorsal plates

  • foot - flat and broad

  • radula - present

  • shell - 8 plates on the shell

  • mass - flattened


Lecture: Annelids and Nematodes


Setae:

  • hair-like projections

  • can be a variety of different things


Closed vs. Open circulatory system:

  • closed:

    • blood runs through the vessels

    • segmentally arranged

  • open:

    • complete digestive system

    • not segmentally arranged

      • clams, gastropods


Compare/contrast leeches v earthworms:

  • leech:

    • blood sucking parasites

    • ectoparasites formally known

    • blade-like jaws to make incision

      • blood taken can be up to 10x body weight

    • used as common medical practice

      • used to treat blood clots

  • earthworms:

    • eat through soil

    • extract nutrients

    • excrete undigested soil

    • hermaphrodites that don’t fertilize


Main features of ecdysozoans:

  • nematodes, arthropods, velvet worms, tardigrades, horsehair worms

  • all have external cuticle

  • molting - names from a process called ecdysis



Ecdysozoan phyla (nematode, nematomorpha, tardigrata, onychophora) description:


Nematodes -

  • many parasitic

  • roundworms

  • complete digestive system

  • no circulatory system


Nematomorpha -

  • horsehair worms

  • brainwash hosts to seek water

  • rarely in vertebrates


Tardigrada -

  • 8 legs

  • found everywhere in water

  • great survivors

  • can survive extreme temperatures, pressure, radiation, outer space, starvation


Onychophora -

  • velvet worms

  • elongate soft bodies

  • predators