zoo 14 exam 1

• Collagen:

  • A tough fibrous protein used to bind cells and tissues together
• Eukaryotic cell:

  • A cell with membrane-bound organelles and a distinct nucleus enclosed by a nuclear membrane
• Genotype:

  • Refers to unique sequence of DNA or genetic component of an organism
• Heterotroph:

  • Eats other plants and animals for nutrients and energy
• Monophyletic:

  • Originates from a common ancestor
• Multicellular organism:

  • Made of many cells with groups of cells differentiating into tissues or organs to perform specialised functions
• Phenotype:

  • Detectable physical expression of the genotype
• Phylogenetic tree:

  • Diagram showing evolutionary descent of different species, organisms or genes from a common ancestor
• Prokaryotic cell:

  • Has no nucleus or membrane-bound organelles
• Animal:

  • Eukaryotic
  • Multicellular
  • Heterotrophic by ingestion
  • No cell wall
• Movement:

  • A fundamental characteristic of an animal
• 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)
• Asexual Development in Animals:

  • Fission: Animal splits its body into two and regenerates all the missing parts
  • Budding: Outgrowth from an animal forms into a new organism
  • Fragmentation: Animal breaks into several parts and new animal forms out of the detached part
  • Parthenogenesis: Formation of an animal from an unfertilized egg
• Sexual Development in Animals:

  • Fertilization: Union of a mature egg cell and sperm cell resulting in a zygote
  • Gastrulation: Germ layers (ectoderm, mesoderm, endoderm) form resulting in a gastrula
  • Cleavage: Mitotic division of the zygote resulting in a ball of cells (morula)
  • Blastulation: Morula becomes filled with fluid resulting in a hollow fluid-filled sphere (blastula)
• Diploblastic:

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

  • Formation of the different organs of the animal body
• Triploblastic:

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

  • Single-celled
  • Size ranges from 0.1-5.0 um in diameter
  • Without nucleus or membrane-bound organelles
  • Circular DNA in the nucleoid region of the cell
  • Enclosed in a cell wall
  • Can have pili, fimbriae or flagella for movement
• Eukaryotic Cell:

  • Size ranges from 10-100 um in diameter
  • With nucleus and membrane-bound organelles
  • Linear DNA is found inside the nucleus of the cell
  • With cytoskeleton for cell shape and organization
  • Animal cells do not have a cell wall
  • Some cells are equipped with cilia
  • The sperm cell has a flagellum
• Endosymbiotic Hypothesis:

  • Eukaryotes developed about 2.7 billion years ago
  • An ancestral prokaryote or proto-eukaryote underwent infolding of its plasma membrane, giving rise to the nucleus and endoplasmic reticulum
  • Endosymbiotic events led to the consumption of aerobic bacteria evolving into mitochondria and a photosynthetic bacterium evolving into a chloroplast
• The origin of eukaryotes involved the consumption of aerobic bacteria, which evolved into mitochondria, and a photosynthetic bacterium that evolved into chloroplasts
• Hypotheses on the origin of multicellularity include:

  • Syncytial or Coenocytial hypothesis: a coenocytic protist with multiple nuclei formed boundaries around each nucleus resulting in a multicellular organism
  • Colonial hypothesis: multicellularity began when an ancestral protist underwent mitosis and its cells remained together as a colony, followed by cellular specialization and infolding to form a two-layered proto-animal
• Syncytial or Coenocytic Hypothesis:

  • The syncytial hypothesis is the traditional term for coenocytic hypothesis
  • It refers to a cell that is multinucleated without boundaries, like the skeletal muscle fiber of animals
• Evolution of animals:

  • First animals appeared over 600 million years ago
  • Nearly all existing animals have obligate multicellularity with body cells undergoing differentiation for specific functions
  • Multicellularity in animals is a result of complex processes from fertilization followed by mitotic division of the zygote
  • Multicellularity in animals is a product of complex and gradual evolution
• Choanoflagellates are the closest living relatives of animals, with a collar complex made of apical flagellum and a collar of microvilli, forming a monophyletic clade "Choanozoa" with animals
• Paths to animal multicellularity:

  • Aggregative Multicellularity: genetically unrelated cells group together in response to adverse conditions, forming an aggregate that neither feeds nor divides, and dissociates once conditions improve
  • Clonal Multicellularity: can arise from failure of cell division to complete cytokinesis, where all cells share an identical genome, providing advantages such as resistance to predators, cooperative feeding, division of labor, and formation of a stable internal environment
• New Hypothesis for Origin of Animal Multicellularity:

  • Sogabe et al. 2019 challenged the colonial hypothesis and homology of animals to choanocytes
  • Proposed hypothesis suggests that the first animal can transition between multiple states similar to present-day transdifferentiating and stem cells
• Animal Bauplan or Body Plan:

  • Refers to a set of characters shared by a group of phylogenetically related animals
  • Can be based on symmetry or number of tissue layers and presence/absence of body cavities
• Hox Genes:

  • Highly conserved family of genes containing homeobox sequences
  • Direct the course of embryonic development and determine the general body plan of an animal, including number of body segments, number and location of appendages, and head-to-tail directionality
• Animal Bauplan Based on Symmetry:

  • Asymmetry: body parts arranged without a central axis (e.g., sponges)
  • Radial symmetry: any plane passing through oral-aboral axis divides the animal into mirror images (e.g., cnidarians)
  • Bilateral symmetry: a single plane passing through the upper and lower surfaces and through the longitudinal axis divides the animal into right and left mirror images (e.g., vertebrates)
• Animal Bauplan Based on Tissue Layers and Body Cavities:

  • Cellular: body is not organized into true tissues but cells are differentiated for specific functions (e.g., sponges)
  • Diploblastic: body parts are organized into layers derived from two embryonic tissues, the ectoderm and endoderm (e.g., cnidarians)
  • Triploblastic: body parts are organized into layers derived from three embryonic tissues, the ectoderm, mesoderm, and endoderm, with most having organ-system level organization (e.g., all other animals)
• Animal Bauplan Based on Tissue Layers and Body Cavities:

  • Acoelomate: body parts derived from three germ layers but no body cavity (e.g., platyhelminths, nemerteans)
  • Pseudocoelomate: body parts derived from three germ layers with a body cavity not entirely lined by mesoderm (e.g., nematodes, rotiferans)
  • Coelomate: body parts derived from three germ layers with a true body cavity surrounded by mesoderm (e.g., molluscs, annelids, arthropods, vertebrates)
• Water consists of two atoms of hydrogen (H) and one atom of oxygen connected by covalent bonds
• Water is polar because its H atoms have partial positive charges while its oxygen atom has a partial negative charge
• Cohesion:

  • Holds water molecules together through hydrogen bonds
  • Allows water molecules to be close to one another and transport water and dissolve nutrients against gravity
• Adhesion:

  • Ability of water to adhere to another substance
  • Makes water an excellent solvent of polar molecules
• High Surface Tension:

  • Water has the greatest surface tension compared to most liquids
  • Allows water to resist an external force
  • Some animals can "walk" on the water surface due to this property
• High Specific Heat:

  • Water has high specific heat relative to other materials
  • Amount of heat a substance must acquire or lose to change its temperature by 1°C
  • Ensures that temperature of water in land and water are within limits that permit life
• High Heat of Vaporization:

  • Amount of heat 1g of liquid has to absorb to change its state to gas
  • Helps moderate the earth's climate as liquid evaporates and cools down the surface
  • Moist tropical air moving poleward releases heat as it condenses to form rain
• Water is a polar solvent:

  • Polar molecules and ionic compounds readily dissolve in water