Lecture 2 Flashcards
What is a cladogram?
way of showing the relationships between different groups (taxa)
What is a sister taxon?
The closest relatives of a taxonomic group
What is the sister group to placental mammals?
Marsupials
What is a monophyletic group?
includes an ancestor and all their descendants (clade)
True or false: Characteristics shared by all extant members of a clade were likely present in their common ancestor
True
What is a paraphyletic group?
includes an ancestor and some their descendants
What is a polyphyletic group?
includes two or more descendants but not their ancestor
What is a clade?
a group that includes a common ancestor and all of its descendants (monophyletic group)
What is a Linnean Taxonomy?
a rank-based ordering system of clades
True or false: Clades are a fact
False. Clades are a hypothesis
What group do chordates belong to?
Deuterostomes
What is our sister group within the animals?
Echinoderms
What is the oldest recognized Chordate in the fossil record?
Pikaia gracilens
How do we decide which species belongs to a clade?
Comparative method: Philosophy
What are common or defining traits of a clade?
A characteristic present in an ancestral species and shared exclusively (in more or less modified form) by its evolutionary descendants
How do lancelets feed?
Filter feed - bury themselves in the ground
what are the 5 chordate synapomorphies?
- Notochord
- Dorsal hollow nerve cord
- Pharyngeal slits
- Postanal tails
- An endostyle (cephalochordates & urochordates) or thyroid (vertebrates) gland (homologous)
Describe the notochord
The notochord is a flexible rod that forms during embryogenesis in all chordates
What is a synapomorphic trait?
does not need to be expressed at every stage of development
What are the three fates of the notochord?
- Cephalochordates: retain a notochord into adulthood
- Primary axial structure that supports their body - Urochordates: have a notochord as larvae but lose it during metamorphosis into adulthood
- Vertebrates: the vertebral column forms around the notochord during embryogenesis
- Species vary in how much of the notochord they retain
How do lamprey feed?
They use their specialized teeth to latch onto and parasitize other larger vertebrates
Trait distinguishing agathas
No jaw
How do hagfish feed?
burrow into and eat the carcasses of dead animals on the bottom of the ocean
3 reasons why hagfish are hard to classify:
Hagfish are a ghost lineage, hard to find, highly specialized
What species are included in cyclostomes?
Hagfish and lamprey
Gnathostomata distinguishing characteristic
Jaw
Chondrichthyes distinguishing characteristic
Cartilaginous fish
Osteichthyes distinguishing characteristic
Boney fish
Actinopterigii distinguishing characteristic
Rays, fins
Sarcoptereygii distinguishing characteristic
Fleshy fins
Lazarus taxa definition
Extant species or taxa that were once thought to be extinct.
What type of breathing do dipnoi do?
bi-modal breathing (they can breathe water (with gills) and air (with lungs))
What clade do all modern amphibians belong to?
Lissamphibia
where must reproduction of Lissamphibia occur?
Lissamphibia must reproduce in or near water
How are amniotes characterized (2)?
by specialized membranes that protect their embryos from water loss, only vertebrates that can live fully terrestrial lives
The four mammalian synapomorphies
Synapsid skull, Hair, Mammary glands, 3 inner are bones
Monotremes distinguishing characteristic (2)
lay eggs, offspring hatch at very immature stage then nurse
Marsupials distinguishing characteristics (4)
give birth to live young, simple placenta, offspring finish developing in pouch where they nurse, short gestation
Eutherian mammals distinguishing characteristic (4)
Well developed placenta, give birth to live young, long gestation, brown adipose tissue
What did the plate tectonics theory predict?
early on in mammalian evolution a small group of mammals were stranded in Africa when that continent was isolated from the others
what is the only extant subclass of the clade Dinosauria?
the Aves
What animal is the only member of their clade (helps understand Sauropsid evolution)
Tuatara
What is the anapsid origin hypothesis?
most sauropods have a Diapsid skull, extant turtles lack temporal fenestrae
Has the Anapsid Origin Hypothesis been refuted and why?
Yes - turtle fossils show that (like sauropods), they once had a diapsid skull have since then lost that trait
