Mammals Flashcards
Aquatic mammals
- Ancestor was terrestrial
- General characteristics retained
- Breath air
- Skeleton more similar to mammals than fish
Integumentary System
Mammals
- Hair
- Horns and antlers
- Glands
Integument = an external covering
Function of hair
- Concealement
- Behavioural signalling
- Waterproofing
- Buoyancy
- Thermal insulation
Hair
Underhair
Soft and dense for insulation (waterproof in aquatic mammals)
Guard hair
Longer and coarse for protection and coloration
Integumentary system
Horns
* Composition:
* Family:
* Shed:
* Branched:
* Function:
- Interior bone & sheath of keratin
- Found in family Bovidae
- Not shed
- Not branched
- Used for social interactions, competition for females
Integumentary system
Antlers
* Composition:
* Family:
* Shed:
* Branched:
* Function:
- Solid bone, no keratin
- Found in family Cervidae
- Only males produce antlers (except in caribou)
- Grow in the spring and shed after breeding season
- Branched
- Used for social interactions, competition for females
* No keratin
Integumentary System
Glands
An organ that secretes a substance that is excreted by the body
Glands
Sweat Glands
- Eccrine glands
- Appocrine glands
Sweat glands
Eccrine glands
- Secrete waterly fluid
- Evaporates on skin and causes cooling
- Occurs in hairless regions in most mammals
- Occurs all over body in humans & horses
Sweat glands
Appocrine glands
- Secrete milky fluid
- Dry on skin to form a film
- Oderless until it combines with bacteria
- Opens into a hair follicle
- Develop near puberty in humans
- Acts as thermoregulation in some mammals, and as phermones in others
Glands
Scent Glands
- Occurs in nearly all mammals
- Communication, marking territory, warning, defense
Glands
Sebaceous Glands
- Secretes sebum into hair follicles
- Keeps skin & hair pliable and glossy
- Covers entire body (most mammals)
- Mostly on scalp & face (humans)
Sebum = greasy mixture
Glands
Mammary Glands
- Produce milk for young
- Occurs in all females
- Secreted via nipples (exc. = monotremes)
Taxonomy
What are the 3 main branches of mammals
- Subclass Prototheria (monotremes)
- Subclass Metatheria (marsupials)
- Infraclass Eutheria (Placental mammals)
Estrous cycle
Estrous = period of heat associated with ovulation
* Monoestrous: single estrus during breeding season
* Polyestrous: recurrence of estrus during breeding season
Menstruation
Discharge of blood and uterine endometrial tissue at the beginning of the menstrual cycle
* Most animals reabsorb the endometrial tissue
* Humans, chimps, elephant shrews and some bats discharge it
Reproductive patterns: Monotremes
- Oviparous
- Large, yolky eggs
- Embryos develop in uterus for 10-12 days
- Thin, leathery shell is secreted around the embryos
- Eggs laid in a burrow or mother’s pouch
- Hatch after 12 more days
- Drink milk produced by mother’s mammary glands
Reproductive patterns: Marsupials
- Sexual
- Dioecious
- Vivparous
- Transient placenta
- Young are born premature
- Gestation is short
- Parental care is long
- Some have specialized pouches where they continue to nurse & protect the young after birth
Reproductive patterns: Placental mammals
- Viviparous
- Prolonged gestation - embryos remain in the uterus nourished by food supplied by the placenta
- Gestation period generally increases with animal size and lifespan
Placenta
The placenta is a modified amniotic egg
* Amnion surrounds embryo with amniotic fluid
* Allantois, yolk sac, and part of chorion contribute to the placenta
* Chorion surrounds entire thing and breaks as labour begins
