1st POST-LAB DISCUSSION (Zoo 102)

• used to represent evolutionary relationship among organisms

  Phylogenetic Tree or Dendrogram
• refers to a derived character state, meaning a trait that has evolved in a lineage from an ancestral state

  Apomorphy
• refers to a shared derived character state, meaning a trait that is shared by two or more taxa and is derived from a common ancestor

  Synapomorphy
• refers to a shared ancestral character state, meaning a trait that is shared by two or more taxa and is inherited from a common ancestor, but is not a derived trait


  Symplesiomorphy
• used to describe the independent evolution of similar traits in two or more taxa

  Homoplasy
• refers to a derived character state that is unique to a single terminal taxon in a data set

  Autapomorphy
• a monophyletic group, made up of an ancestor and all of its descendents


  Clade
• represents the course of evolutionary history and the pattern of descent—the transfer of genetic material from parents to offspring over time of a group of organisms

  Phylogeny
• root of the tree represents the?

  ancestral lineage
• the tips of the branches represent the?

  descendants of that ancestor
• refers to the origin of a particular species or group of organisms

  Ancestry
• When a speciation event occurs, a single ancestral lineage splits and gives rise to two or more daughter lineages—represented as branching on a phylogeny.

  A) Speciation Event

  B) Ancestral Lineage
• Where a tree branches, there is a speciation event.
• Characters are morphological or molecular features that are mostly genetically determined and are heritable. Relatively, characters are invariable within an operational taxonomic unit (OTU) such as a taxon.
• A named group of organisms

  Taxon
• Characters in a phylogenetic tree

  A) plesiomorphy

  B) symplesiomorphy

  C) synapomorphy

  D) autapomorphy

  
• the earlier or ancestral state of character thus, is the original or primitive condition.

  Plesiomorphy
• Symplesiomorphy


  refers to the shared ancestral condition which is different from plesiomorphy
• Apomorphy


  refers to the later or descendant state after transformation of the original condition to its derived or changed condition
• Synapomorphy


  shared changed condition
• Autapomorphy


  unique characteristics of a lineage
• Homology is a term wherein features of two or more different organisms having common ancestry/origin.
• Homologous structures are structures similar between successively repeated parts in the same organisms.
• The scientific name for Amphioxus is Branchiostoma lanceolata.
• Amphioxus is also known as lancelet.
• Amphioxus is a small, primitive, marine chordate belonging to the subphylum Cephalochordata.
• Identify the parts of the amphioxus.

  A) Oral Hood

  B) Buccal Cirri

  C) Hatschek's pit

  D) Wheel organ

  E) Velum

  F) Pharyngeal slits

  G) Notochord

  H) Endostyle

  I) Midgut caecum

  J) Dorsal tubular nerve chord

  K) Hindgut

  L) Iliocolon ring

  M) Intestine

  N) Anus

  O) Caudal end (post-anal tail)

  
• Identify its parts.

  A) Ocellus

  B) Notochord

  C) Velar tentacle

  D) Wheel organ

  E) Velum

  F) Hatschek's pit/groove

  G) Oral hood

  H) Pigment spot

  I) Buccal cirri

  J) Endostyle

  
• Identify the parts of amphioxus c.s.

  A) Dorsal Ridge/Fin

  B) Dorsal tubular nerve chord

  C) Notochord

  D) Pharyngeal bars

  E) Pharyngeal slits

  F) Pharynx

  G) Caecum

  H) Endostyle

  I) Metapleural folds

  J) Testis

  K) Metapleural folds

  L) Ovary

  M) Myosepta

  N) Myomeres

  
• Differences in Circulatory System: The amphioxus lacks a heart.
• Difference in Circulatory System: composed of vessels and tissue channel that forms a continuous circuit.
• Difference in Circulatory System: Blood is colorless.
• Difference in Nervous System: It lacks brain (vertebrates are the only chordates that have the brain as part of the central nervous system).
• Differences in Bony Skeletal Elements: They have no vertebral column and no cranium or skull.
• Similarities with Vertebrates:

  1. Notochord
  2. Pharyngeal slit
  3. Dorsal Nerve Cord
  4. Endostyle
  5. Postanal Tail
  6. Myomeres/segmented muscles
  7. Gut Structure
• Vertebrate Morphogenesis:

  1. Gametogenesis
  2. Fertilization
  3. Cleavage
  4. Gastrulation and Neurulation
  5. Organogenesis
  6. Germ layer Derivatives
• It is the process by which the two gametes (male and female) fuse to become a zygote. May be internal or external.

  Fertilization
• This type of gametogenesis starts early adolescence, and is more differentiated.

  Oogenesis
• This type of gametogenesis starts upon birth.

  Spermatogenesis
• Spermatogenesis starts with diploid spermatogonia, which divide by mitosis to produce more spermatogonia and primary spermatocytes. The primary spermatocytes then undergo meiosis I to produce two haploid secondary spermatocytes, which further divide by meiosis II to produce four haploid spermatids. The spermatids then undergo spermiogenesis, a process of remodeling and differentiation into mature spermatozoa. The entire process takes about 70 days.