Lecture 20 - Mammals Flashcards
Mammals: what is the definition, what groups are there, how many species are there, and where can they be found?
Hair, three bones in the inner ear, and milk produced through modified sweat glands
Placental, marsupials, monotremes
~5,000 species
Everywhere globally (excluding inland Antarctica)
Monotremata: what are they, how many species are there, and where are they located?
Protheria - egg-laying mammals
Only five extant: platypus and four types of echidna
Australia and new guinea
Echidna penis
Multi-headed (4) and only uses one head at a time
Marsupials: what are they, how many species are there, where did they originate from, and what are any significant features?
Mammals that birth their young prematurely and keep them in a pouch where they grow
353 species, mostly in Australia and SA (1 in NA)
Originated in South America and spread to Australia via Antarctica and to North
America (although they became mostly extinct here ~20mYa) and Europe
- All large carnivorous marsupials in South America have disappeared
- Sperm enters via lateral vaginas; embryo descends through middle vagina
- Not clear what advantage of being
a marsupial is…
Possums vs Opossums
Split around 80mYA
Opossums - found in America, only marsupial in NA
Possums - found in new guinea, Australia, Sulawesi
Gollum Opossum: what are they, where are they found, and what is a significant feature?
A semi-aquatic opossum that swims with its arms outstretched to catch shrimp and fish
Found in central/south America
- Males tuck their genitalia into a pouch before swimming
- Sleep for 18 hours on average, like all Opossums
Mammals: what is the species breakdown?
Rodents - 2000 species
Chiroptera - 1240 species
Soricomophora (shrews etc) - 400 species
Other (including primates and Carnivora) - the rest
Rodents: what types are there and how extinct are they?
- Sciurognathi (squirrel-like / mouse-like rodents)
- Hystricognathi (cavies, capybara, mole-rats etc)
- Synapomorphies: Contain a single pair of continuously-growing incisors, no canines, Trough-like mandibular fossa (where the temporal bone articulates with the lower jaw), NOT including rabbits (Lagomorpha) or shrews
At least 54 species have gone extinct in the last 200 years
~80 are critically endangered (< 250 individuals)
Chiroptera: what are the examples, how many species are there, and what key features do they have?
Megachiroptera (‘Megabats’): fruitbats and flying foxes (eat fruit or nectar)
Microchiroptera (‘Microbats’): largely insectivorous, echolocating, originated around 50 MY ago, when the climate warmed substantially, plant diversity, peak insect diversity
17 families with over 900 species
- Up to 1.7m wingspans, navigate by sight (though crepuscular)
- Microchiroptera probably paraphyletic
- You are as closely related to a bat as a bat is to a mouse (split about 94 million years, in both cases)
- Global distribution
- The fourth phylum to gain powered flight
- Light slender skeleton, wings are homologous to hands
- Wings also extend to hind legs – used for manoeuvre and prey
- Bat wings are covered with tiny bumps (Merkel cells) that contain touch-sensitive receptors which help in flight
Echolocation
Given the phylogenetic tree, looks like a case of
convergent evolution as sea mammals and bats do it despite having other closer species without it
* 2013 study of 800,000 amino acids in 22 mammals, suggests the same genes are involved each time – genes linked to hearing/deafness and vision
Sperm competition in flying foxes
Male-male competition for females
- Produce more sperm to drive out competitor sperm
- Large testes in species with male-male competition, or possibility of female promiscuity
Whales: what types are there, how many species and what key features are there?
Baleen (Mysticeti) or Toothed (Odontoceti) whales
90 species
- Blue whale heart is 2m tall and is almost as big as a small car
Primates: what types are there, how many species are there, and what are some key features?
- Strepsirrhini – non-tarsier prosimians (wet nose,
median groove in the nose, shiny eyes) - Haplorhini – tarsiers, simians (dry nose, broad
nostril narrows at the top) - Simians: Catarrhini (apes, Old World monkeys) and Platyrrhini (New World monkeys)
> 360 extant species
- Appeared around 65 mya
- Found mainly in central America, Africa, and Madagascar (tropical rainforests)
- 25 new species have been found this century
Madagascan mammals: what mammals are there, how did they arrive in Madagascar, how many species are there, and what did human intervention due to them?
An extraordinary range of 100 species of Strepsirrhini (lemur) and several other mammals (either terrestrial or marine)
1) Island separated from Africa (160 MY), then Antarctica then India
2) Around 60 MYa, early primates rafted over, by chance - the Simpson: ‘sweepstakes hypothesis’ (lucky) as currents at the time in the right direction would mean only a 30-day journey
3) All lemurs descended from this event; also the arrival of mongoose-like carnivores (15 MY) – 12 species, including catlike fossa
- Almost all mammals are endemic to Madagascar
and fill niches that are occupied in the rest of the world - These mammals mainly thrive due to no Haplorhini (monkeys) being present in Madagascar
Human arrival 2000 years ago resulted in the extinction of at least 15 species
Megafauna
Large animals in the area they are in (elephants, for example)
Mainly stable in Africa and south-east Asia for the last 8,000 years but large numbers of megafauna have become extinct in the Americas and Oceania
