Mammalian Origins And Characteristics Flashcards Preview

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Flashcards in Mammalian Origins And Characteristics Deck (17)
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1
Q

How many mammal and bird species are there?

A

Mammal: around 4,500

Birds: 10,000

2
Q

What are the characteristics that define mammals?

A

They give birth to live young

They produce milk from mammary glands

They have hair of some description

3
Q

What is an amniote?

A

A tetrapod vertebrate with a membrane, water-proof, shelled egg

4
Q

What is anapsid, synapsid and diapsid?

A

Anapsid: no temporal fenestra/no hole in the skull

Synapsid: single fenestra/ one hole (humans)

Diapsid: double fenestra/two holes in the skull

5
Q

What is a cladogram?

A

A branching diagram showing the cladistic relationship between a number of species

6
Q

What do the nodes in a cladogram define?

A

The synapomorphies= the shared derived character states

7
Q

What was the first grouping of mammal-like reptiles called?

A

Pelycosaurs

8
Q

When were Pelycosaurs abundant?

A

The Late Carboniferous/early Permian (320-265mya)

9
Q

What were the characteristics of Pelycosaurs?

A

Parasagittal gait compared to other reptiles- different walking style

Primitive heterodonty (different teeth)

Relatively long limbed

Elongated neural spines on the vertebrae to help with weight bearing

10
Q

Give an example of a dinosaur with neural spines?

A

Dimetrodon limbatus

Larger of the species and were top predators

Carnivores

11
Q

How did the neural spines act as thermoregulation?

A

Allowed the organism to warm up quickly in the morning

Large SA to allow heat to dissipate easily

May have an angled sail away from the sun to cool down or alter blood flow to keep warm at night

12
Q

When did therapsids occur and what characteristics did they have?

A

Late Permian before break up of Pangea

Longer lumber, more upright stance, rib reduction and perhaps had a diaphragm

13
Q

What are the characteristics of Cynognathus crateronotus?

A

Very large and powerful head

Incisors, canines and cheek teeth for a carnivorous diet

Likely to be warm blooded

Consumed herbivorous reptile therapsids

14
Q

What are the characteristics of cynodonts?

A

Reduced rib structure (loss of lumbar ribs)

Secondary palate- allows animal to breathe while eating and could be a heat exchanger

Greater heterodonty

Zygomatic arch to give more force to their bite

15
Q

What are some defining nodes (synapomorphies) in the cladogram for mammals?

A

Enlarged dentary- bigger lower jaw

Prismatic enamel tooth surface- longer wearing teeth

Dentary squamosal jaw articulation

Tribosphenic cheek teeth

Placenta

16
Q

What are tribosphenic cheek teeth?

A

They’re very deep rooted and the upper and lower teeth fit together very well

Important they have precise eclusion- they fit together

17
Q

What makes characters homologous?

A

Common ancestry