Mammals

Class

Mammalia.

Serenia ( Dugongs and Manatees)

Cetacea (Whales and porpoises)

Characteristics

Hard bony skeletons.

Unique traits: Three ear bones (malleus, incus and stapes). Presence of hair (dead keratin). Mammary glands for milk production.

Not unique: endothermic (maintain body temperature by producing metabolic head). Vivipary. Internal fertilization (most have placenta). 4 chamberef heart. Extreme parental (most maternal) care.

Skin

No feathers or scales. However it does shed cells and does have hair.

Hair/Fur

Protein filament that grows from the skin. Amount of hair varies greatly between species. Heat insulation. Sensory information: touch and movement (sensory hairs on faces called whiskers). Hair coloration: camouflage.

Lactation

The ability to produce milk to nourish their young - increases their chances of survival.

Placenta and vivipary

1. Placenta: organ that connects the developing embryo to the mother. 94%.

2. Vivipary: retention and growth of fertilized egg within the maternal body until the young animal is capable of independent existence

Non placental mammals

1. Monotremes: basal, egg laying.

2. Marsupials: characterized by front pouches used to protect their newborn offspring.

Homoplasy

Form and function are closely tied together. Related organisms develop dissimilar structures. Divergence in similar animals that live in very different habitats/have different life styles.

Different habitats can lead to dissimilar features in animals which are closely related. Those features have the same origin.

Analogue

Form and function are closely tied together. Unrelated organisms develop similar structures. Convergence is very different animals that live in similar habitats or have similar life style.

Similar habitat can lead to similar features in animals which are not closely related. Those features dont have the same origin.

Ecological diversity

Mammals have colonized all continents including inhospitable environments.

Have evolved physiologically and neurologically diverse adaptions.

In ecosystem provide essential services I.e seed dispersal, pollination and regulating insect populations

Cetaceans

Whales. Smooth streamlined shape and no hind limbs. Odontocetes (toothed whales) and mysticetes (baleen whales). Share ancestry with hippos.

Vestigial structurs

Organs or anatomical structures that have been retained during evolution even though they lost some of their ancestral function.

Both cetaceans and sirenians lack hind limbs but have pelvic bones

Marine mammals adaptions

Streamlined bodyshape. Flipper shaped fore limbs.

Obligated swimmers: species that spend its entire life in water. Have wide flat muscular tails. Little hair.

Non-obligated swimmer: on land and in the water. Webbed limbs. Hind limbs. Dense thick fur coats.

Generating heat

Endothermy (process of generating heat from the chemical digestion of food). Homeostasis (condition of a body that is actively regulated to remain constant).

-by shivering or increases its metabolic rate of converting food energy to heat.

Problem: ocean water is colder than internal body. Some live in polar climates or dive deep into cold waters.

Retaining heat

Insulating layers - blubber (dense layer of fat tissue under the skin of most marine mammals)

-Fur

Diving

All mammals need to breathe to provide oxygen to cells. Unlike fish, marine mammals do not have gills to extract oxygen directly from the water.

Lack of oxygen while diving decreased metabolism and a larger reliance on anaerobic respiration which lead to accumulation of toxic lactic acid byproduct. More enzymes to break down lactic acid.

Increased the amount of oxygen that can be stored in lung, muscle and blood. Higher concentrations of hemoglobin and myoglobin. Increased blood volume.

Communication

Center of social interactions. Visual, touch, smell, sound. Most effective means in water is sound which can travel longer distances and is fast.

Visual (limited by visibility and by availability of light)

Smell (not effective in water. Chemical molecules diffuse rapidly in water)

Ecolocation

Process of emitting sound and listening to the sound echoes returning from nearby objects.

Sounds useful for navigation and locating prey.