Lecture 1. Evolution of Animals

• a tough fibrous protein used to bind cells and tissues together


  collagen
• a cell with membrane-bound organelles and a distinct nucleus enclosed by a nuclear membrane

  eukaryotic cell
• refers to a unique sequence of DNA or genetic component of an organism

  genotype
• eats other plants and animals for nutrients and energy

  heterotroph
• originates from a common ancestor

  monophyletic
• made of many cells with groups of cells differentiating into tissues or organs to perform specialised functions

  multicellular organism
• detectable physical expression of the genotype

  phenotype
• diagram showing evolutionary descent of different species, organisms, or genes from a common ancestor

  phylogenetic tree
• has no nucleus or membrane-bound organelles

  prokaryotic cell
• • present-day bacteria

  • live in different environments (e.g. soil, water, and other organisms)

  eubacteria
• all organisms whose cells have nucleus and membrane-bound organelles

  eukaryota
• Live in extreme environments (e.g. hot sulfur springs)


  archaebacteria
• • derived from the Latin word anima, which means “breath”

  • eukaryotic

  • multicellular

  • heterotrophic by ingestion

  • no cell wall

  animal
• Movement is a fundamental characteristic of an animal.

  Ex. In vertebrates,

  • every cell that is involved in the movement is controlled by the nervous system

  • The somatic nervous system controls cells involved in voluntary movement

  • The autonomic nervous system controls cells involved in involuntary movement
• Animals produce collagen.

  ‣ a connective tissue

  ‣ a structural protein that binds cells, tissues, and organs

  ‣ consists of three pro-collagen molecules that twist into a helix

  ‣ errors in genes encoding collagen can result in collagen tissue diseases (e.g. rheumatoid arthritis)
• Animals can reproduce sexually or asexually.
• (Asexual Development in Animals)

  • Animal splits its body into two

  • Regenerates all the missing parts


  Fission (example: sea anemone)
• (Asexual Development in Animals)

  • Outgrowth from an animal forms into a new organism


  Budding (example: Hydra)
• (Asexual Development in Animals)

  • Animal breaks into several parts

  • New animal forms out of the detached part


  Fragmentation (example: sea star)
• (Asexual Development in Animals)

  • Formation of an animal from an unfertilized egg


  Parthenogenesis (example: honey bees producing drone)
• (Sexual Development in Animals)

  • Union of a mature egg cell and sperm cell

  • Results into a zygote


  Fertilization
• (Sexual Development in Animals)

  • Germ layers (ectoderm, mesoderm, endoderm) form

  • Results into a gastrula


  Gastrulation
• (Sexual Development in Animals)

  • Mitotic division of the zygote

  • Results into a ball of cells (morula)


  Cleavage
• (Sexual Development in Animals)

  • Morula becomes filled with fluid

  • Results in a hollow fluid-filled sphere (blastula)


  Blastulation
• (Sexual Development in Animals)

  • Formation of the different organs of the animal body

  Organogenesis
• (Sexual Development in Animals: Organogenesis)

  • Animal has only two germ layers (ectoderm & endoderm) that give rise to its organs


  Diploblastic (example: hydra)
• (Sexual Development in Animals: Organogenesis)

  • Animal has all three germ layers that give rise to its organs

  Triploblastic (examples: flatworm, annelid, nematode)
• (Spontaneous Formation of First Organic Molecules from Inorganic Molecules)

  • Water (H2O) evaporated into an atmosphere with methane (CH4), ammonia (NH3) and hydrogen gas (H2)

  • Electrical discharges were released into this mixture of water vapour and gases

  • Led to the formation of simple organic compounds like amino acids

  • Provided first evidence that organic molecules required for life could have formed from inorganic compounds

  Stanley Miller - Harold Urey Experiment (1953)
• Formation of Macromolecules (Cooper, 2000)

  •the monomer building blocks of macromolecules attach spontaneously (e.g. amino acids polymerize to form protein)

  •key feature of the macromolecule from which life evolved has to be its ability to copy itself, which will allow it to reproduce itself and evolve through time
• Formation of Macromolecules (Cooper, 2000)

  •In the 1980s S. Altman and T. Cech found out that (RNA) could copy itself

  ✓Thus, RNA must be the first genetic material before the appearance of the DNA
• • pro “before” + karyon “nucleus”

  • appeared before eukaryotic cells

  • single-celled

  • size ranges from 0.1-5.0 um in diameter

  • without nucleus or membrane-bound organelles

  • with circular DNA in the nucleoid region of the cell

  • enclosed in a cell wall

  • can have either pili, fimbriae, or flagella

  • pili are used for the exchange of genetic material during conjugation, a form of reproduction

  • flagella are for movement

  A) Cell wall

  B) Cell membrane

  C) Ribosome

  D) Chromosom/DNA

  E) Nucleoid region

  F) Flagellum

  G) Capsule

  H) Pili

  
• • eu “true” + karyon “nucleus”

  • size ranges from 10-100 um in diameter

  • with a nucleus and membrane-bound organelles “little organs”

  ✓compartmentalization allows efficient function

  • linear DNA is found inside the nucleus of the cell

  • with the cytoskeleton, a skeletal framework provides cell shape allows organization of the cytoplasm, and facilitates intracellular movement

  A) Lysosome

  B) Golgi apparatus

  C) Rough ER

  D) Smooth ER

  E) Nucleolus

  F) Nucleus

  G) Centrioles

  H) Microtubules

  I) Cytoplasm

  J) Ribosome

  K) Mitochondrion

  L) Plasma membrane

  
• ✓do not have a cell wall

  ✓some cells are equipped with cilia

  ✓the sperm cell has a flagellum

  Animal Cell
• Evolution of Eukaryotes (Cooper, 2000)

  •eukaryotes developed about 2.7 billion years ago (BYA)

  •most popular hypothesis is the endosymbiotic hypothesis

  ✓ According to this an ancestral prokaryote or proto-eukaryote underwent infolding of its plasma membrane, which gave rise to the nucleus and endoplasmic reticulum.

  ✓ In the course of its evolution, the ancestral eukaryote underwent endosymbiotic events.
• Evolution of Eukaryotes (Cooper, 2000)

  • Endosymbiotic events that happened in the ancestral eukaryote after developing nucleus and endoplasmic reticulum:

  i. It consumed aerobic bacteria, which evolved into the mitochondria

  ii. It consumed a photosynthetic bacterium that evolved into a chloroplast

  • These events gave rise to the modern-day eukaryotes.
• (Hypotheses on the Origin of Multicellularity)

  ✓suggested that a coenocytic protist with multiple nuclei formed boundaries around each nucleus resulting in a multicellular organism.

  Syncytial or Coenocytial hypothesis
• (Hypotheses on the Origin of Multicellularity)

  ✓suggested that multicellularity began when an ancestral protist underwent mitosis and its cells remained together as a colony

  ✓this colony underwent cellular specialization

  ✓this is followed by infolding to form a two-layered proto-animal

  Colonial hypothesis
• What hypothesis does the diagram show?

  A) Syncytial hypothesis

  
• Syncytial or Coenocytic Hypothesis

  • The syncytial hypothesis is the traditional term for the coenocytic hypothesis.

  ✓It used the term “adj. syncytial” or “noun. syncytium”, which means that the cell is multinucleated without boundaries.

  ✓An example of a syncytial cell is the skeletal muscle fiber of animals, which is multinucleated
• What hypothesis does the diagram show?

  A) Colonial hypothesis