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Mr. McCloskey Biology II Class Mammalia Mammals
Threatened and Endangered Species of PA 8&q= &q=150321
Mammals ► Came into being around 200 million years ago – flourished to around 70 million years ago ► Although not a large group (approximately 4450 species) it is overall the most biologically differentiated group in the animal kingdom.
Mammals ► Mammals probably have been influenced by humans more than any other group of animals. ► Mammals have been domesticated for clothing, as beasts of burden, and as pets.
Mammals ► Millions used in biomedical research each year.
Mammals ► Mammals have been introduced into new habitats (with both positive and negative results)
Mammals ► Mammals have led to the destruction of habitats for commercial uses.
Mammals ► Some animals have been greatly over harvested.
Characteristics ► Body covered with hair (Reduced in some species, especially aquatic ones).
Skin with many glands ► Sweat glands – not present in any other vertebrates ► Scent glands - found in nearly all mammals although functions vary greatly. Used by some species for communication, to mark territory, for warning and for defense.
Skin with many glands ► Sebaceous glands – sometimes called oil glands ► Mammary glands – produce milk for nourishing young.
Limbs ► Four limbs- (reduced or absent in some) adapted for many forms of locomotion
Heart ► Four chambered heart with 2 atria and 2 ventricles
► Warm blooded
Teeth ► Well developed teeth ► Teeth will be adapted for specific diet ► 4 types of teeth found in mammals Incisors = Flat, sharp edges, used for snipping, cutting and gnawing.
Teeth ► Canines = long and pointed, used for tearing and piercing
Teeth ► Premolars = compressed square shape, for shearing and slicing
Teeth ► Molars = Large bodies, squared also, used for crushing and grinding
Teeth ► Types of teeth present and size will vary according to the animal’s needs. ► Most mammals grow just two sets of teeth. Deciduous teeth Permanent teeth
Teeth ► Permanent teeth = Grow in when the skull has grown large enough to accommodate a full set (Molars only come in with other permanents – not present in deciduous set)
Lungs ► Mammals use lungs to breath for their entire life.
Highly Developed Brains ► Especially well developed in primates. 3 major regions Cerebrum – Largest portion, controls voluntary functions Cerebrum – Largest portion, controls voluntary functions Cerebellum – Balance, involuntary actions, muscle coordination Cerebellum – Balance, involuntary actions, muscle coordination Medulla oblongata – vital body processes such as breathing and heart beat Medulla oblongata – vital body processes such as breathing and heart beat
3 Lines of Mammal Development ► 1) Monotremes ► Egg-laying mammals – mothers have no nipples ► Only 3 species exist – Duck-billed Platypus and 2 spiny Anteaters ► They live in Australia, New Guinea and Tasmania
Marsupials ► Marsupials ► Pouched mammals ► Give birth to tiny young which are effectively still embryos both anatomically and physiologically ► Must crawl to mother’s pouch to complete development ► Found mainly in Australia, opossum is the only native North American species
Placental Mammals ► Most highly evolved animals on Earth ► Carry unborn young in the uterus – nourished by the placenta ► Materials transferred from mother to unborn young through the umbilical cord ► The period of time that young develops in placenta is called the Gestation Period – This will vary from mammal to mammal ► (Mouse – 21 days, rabbit days, horse – 48 weeks, elephant 22 months)
Threatened or Endangered Species ► sp?a=458&q= sp?a=458&q= sp?a=458&q=150321