Mammals Flashcards
1
Q
What are the general characteristics of mammals?
A
- Body covered with hair Reduced in some - Great variety of integumentary glands - Endothermic - Dioecious - Highly developed olfactory sense (smell) - Most viviparous (placental) Notable exception: monotremes are oviparous
2
Q
Why are they interesting?
A
- Because we are ultimately most interested in ourselves
- They are very cute
- Intriguing reproductive strategies
3
Q
Explain how they went from sea to land
A
- Amniotes are adapted to land
- What about aquatic mammals?
- May depend partly or entirely on aquatic environment
Even for fully aquatic mammals, ancestor was terrestrial
General characteristics of mammals retained
Breathe air
Skeleton more similar to mammals than to fish
4
Q
Explain the basics to mammals
A
- Approx. numbers of species
Mammals 5,400
Birds 10,000
Fish 28,000
Insects 1,100,000
- Very diverse in size, shape, form and function
For example...
Flying terrestrial Kitti's hognose bat (2g)
Aquatic blue whale (170 metric tons)
5
Q
What are the three groups of mammals?
A
- Monotremes: egg laying mammals (platypus)
- Marsupials: pouched mammals (kangaroo, koala, opossums)
- Placental mammals (everything else)
6
Q
What is the integumentary system?
A
- Role in protection
- Comprised of skin and appendages
- An external covering
- Integumentary system distinguishes mammals as a group
- We’ll cover: hair, horns/antlers, glands
7
Q
Explain the hair
A
- All mammals have hair, and all animals with hair are mammals
- Diverse uses for hair
Concealment
Behavioural signalling
Waterproofing
Buoyancy
Thermal insulation - Cetaceans (whales, dolphins, porpoises)
Sensory bristles on snout
These are lost before or short after birth - Mammals characteristically have two kinds of hair
Underhair is soft and dense (for insulation)
Guard hair is longer and coarse (protection and coloration) - In aquatic mammals
Seals, otters, beavers, polar bears
Underhair is extremely dense and does not get wet - Guard hair gets wet and forms a protective layer over the underhair
8
Q
What is hair made of?
A
- Dead epidermal cells containing keratin
Keratin is a fibrous structural protein
9
Q
What is the shedding in mammals?
A
- Human lose (and regrow) hair continuously through life
- Most mammals have two annual molts (spring and fall)
Summer coats are thinner than winter coats
Can be different colour
10
Q
What are examples of modified hairs?
A
- Porcupine quils
- Vibrissae (whiskers) on the snout of mammals
Well innervated airs that specialized for tactile sensing
Occur in most mammals but not in humans
Especially long in nocturnal and burrowing animals
11
Q
Explain the horns
A
- True horns have two parts
Interior none
Sheath of keratin
- Found in members of family Bovidae
- Not shed
- Not branched (antlers are)
- Used for social interactions, competition for females
12
Q
Explain their antlers
A
- Composed of solid bone
No keratin
- Family Cervidae (moose, deer, caribou)
- Generally, only males produce antlers
Caribou are an exception
- Shed
Grown in the spring and shed after the breeding season
- Branched
- Used for social interactions, competition for females
13
Q
What are their glands?
A
- It’s an Orhan or group of cells that secretes a substance that is used or excreted by the body
- Great variety of integumentary glands
- Four classes (all associated with the epidermis)
Sweat
Scent
Sebaceous
Mammary
14
Q
What are sweat glands?
A
- Occur over much of the body surface in most mammals
Absent from other vertebrates - Eccrine glands
Secrete watery flui
Evaporates on skin and causes cooling
Occur in hairless regions in most mammals
Occur all over the body in humans and horses - Apocrine glands
Secrete milky fluids that dry on skin to form a film (odourless until it combines with bacteria)
Open into a hair follicle
Develop near puberty in armpits, groin, breasts, and external auditory canals (in humans)
Acts in thermoregulation in some mammals and as a pheromone in others
15
Q
What are scent glands?
A
- Occur in nearly all mammals
- Used for
Communication, marking territory, warning, defence - Most mustelids (skunks, minks, weasels) have scent glands that open by ducts to the anus
- Most odoriferous of all glands
16
Q
What are scent glands?
A
- Usually associated with hair follicles
- Secreted cells expel a greasy mixture called sebum into hair follicle
- Keeps skin and hair pliable and glossy
- Most mammals have sebaceous glands covering entire body
- In humans they are mostly located on scalp and face
17
Q
What are mammary glands?
A
- Produce milk for young
- Occur on all female mammals
Rudimentary form on male mammals - In most mammals, milk is secreted from mammary glands via nipples
Monotremes lack nipples
Milk is secreted onto the fur of the mothers belly where the young lap it up
18
Q
How is there food and feeding?
A
- Mammals exploit a wide variety of food sources
- Four basic trophic categories
Insectivores
Carnivores
Omnivores
Herbivores - But many subcategories
These four categories don’t adequately describe all mammalian feeding habits - Trophic = relating to nutrition
19
Q
Explain the insectivorous mammals
A
- Feed on insects and other small invertebrates
- Usually small
Shrews, moles, anteaters, bats - Intestinal tract tends to be short
Eat little fibrous vegetal matter (which requires prolonged fermentation) - Teeth with pointed cusps for piercing exoskeleton
Exception: anteater (has no teeth, uses tongue)
20
Q
Explain the herbivorous mammals
A
- Feed on grasses and other vegetation
- Two main groups
Browsers and grazers: hooded mammals
Gnawers: many rodents - Canines are absent or reduced in size
- Molars and premolars are adapted for grinding
- Rodents (beavers) have chisel sharp incisors
Grow throughout life and must be worn away through use - Adaptations for fibrous diet
- No vertebrates synthesize cellulose splitting enzymes
Cellulose = structural carbohydrate in plants - Herbivores generally have long digestive tracts and need to eat a large quantity of food to survive
21
Q
How do we break cellulose into glucose?
A
- Anaerobic bacteria and unicellular eukaryotes produce celluloses in the gut
- These enzymes can break down cellulose via fermentation
22
Q
What are ruminants?
A
- Herbivores with a large four chambered stomach
Cattle, goats, deer, giraffes - Grass passes down the esophagus to the rumen
Digested by microorganisms in rumen - Ruminator returns cud to its mouth, and re chews it
- Returns to the rumen where it undergoes a second round of fermentation
- Then carries on through the “true stomach” (abomasum) where normal digestion occurs
23
Q
Explain the carnivorous mammals
A
- Mainly feed on vertebrates, molluscs, crustaceans
Foxes, dogs, weasels, wolverines, seals, cats - Shearing and piercing teeth, and powerful claws
- Digestive tract is shorter (meat is more easily digested)
- Feed in discrete meals
Rather than continuously like herbivores - More leisure time, but also more active
- Can survive for a long time without food
e.g. wolves can go for days or even weeks without eating
24
Q
Explain the omnivorous mammals
A
- Use plants and animals for food
e.g. pigs, raccoons, many rodents, bears, most primates - Versatile dentition for a varied diet
- Even some carnivores often will eat fruits, berries, grasses
Opportunistic
Categories are not always completely clear
25
Q
What is their territory?
A
- Many mammals have territories
Areas from which individuals of the same species are excluded - Mammals mark boundaries of their territories with secretions from scent glands, and with faces or urine
- Territories vary greatly in size depending on size of animal and its feeding habits
- Advantages of a territory
Interruption free mating
Reduce competition for food (particularly when raising young)
Reduce overcrowding
26
Q
What is home range?
A
- A larger foraging area surrounding a defended territory
- Can overlap with other individuals of the same species
27
Q
What is the taxonomy of living mammals?
A
- 29 recognized orders
- Phylum: Chordata
- Class: Mammalia
28
Q
What are the 3 main branches?
A
Subclass: Prototheria (Monotremes)
Subclass: Metatheria (Marsupials)
Infraclass: Eutheria (Placental Mammals)
29
Q
Explain the subclass Prototheria
A
- Oviparous mammals
- Duck billed platypus and echidna
30
Q
Explain the subclass Metatheria
A
- American opossums
- Koala, wombats, possums, wallabies and kangaroos
31
Q
Explain the infraclass Eutheria
A
- Many groups
