Mammals - Characteristics, Origin & Evolution
The lower jaw bone of a mammal is composed of how many bones?
1
How do reptiles control their body temp?
Absorb heat from surroundings
What structures allow a much larger surface area for gas exchange in the lungs of mammals?
Alveoli
With what specific characteristic can synapsid & mammal fossils be identified?
An opening in the skull, behind the eye socket
What is the function of the front teeth?
Biting, crushing, seizing prey
The placenta contains tissues from ____ from both ____ & _____
Blood vessels Mom & baby
In the brain, mammals have much larger ____ than reptiles of the same size
Cerebrum
2 groups of vertebrates that appeared at about the same time during the Triassic period were
Mammals & dinosaurs
Milk is produced by _____ glands, and contains what nutrients?
Mammary fats, proteins, sugars
When were the 3 main groups of modern mammals develop?
Middle of Cretaceous period (144-6 MYA)
What are mammary glands?
Modified sweat glands located in thorax or abdomen
What are those 3 main groups?
Monotremes, marsupials, placental mammals
?What is the advantage of having a heart with 2 separated ventricles?
More efficient pumping of blood through both circuits of the system
Which modern mammal did Eozostrodon look like?
Mouse
What can diffuse across the placenta between the mother and baby?
Nutrients, waste, gases
List 4 characteristics of the early synapsid, Dimetradon
Opening behind eye in skull Sail-like structure on back Specialized teeth ??
What is a monotreme?
Oviparous (lay eggs)
Why is having 2 separate ventricles in their heart so important for mammals?
Oxygen requirement demands no dilution of blood
Define Endothermy
Produce body heat through metabolism
How do mammals control their body temp?
Produce heat internally by metabolism
What is it important when trying to identify vertebrae fossils?
Reptiles have several bones in jawbone, mammals only have one
What is a diaphragm & what is its function?
Sheet of muscle below rib cage that draws air into lungs, increases efficiency
How are mammals constantly losing heat?
Skin & breath
What specific advantage does chewing food offer a mammal?
Speeds up digestion
What are some modifications we see in mammal teeth?
Teeth in different parts are modified for special functions
What is the chorion?
The outer membrane that surrounds the egg
What was the group of synapsids that gave rise to the modern mammal?
Therapsids
What is Baleen?
Thin plates of fingernail like material that hang from roof of the mouth
The heart of a mammal has ____
Two completely separate ventricles
What are characteristics of reptile teeth?
Uniform in size & shape regardless of where they're located
What is echolocation & what can it be used for?
Using high frequency sound waves that bounce off objects to determine size, distance, direction & speed of the object
Life 4 characteristics about marsupials?
Very short period in mother Emerge from uterus very small Crawl into pouch and attach to nipple Growth continues until ready to survive outside pouch
Marsupial
Viviparous - live young but development in mother is short
The placenta is an extension of the ____
chorion
Variations in the way an animals teeth are positioned depend on its ____
diet
Early mammals are thought to have avoided competition with dinosaurs by feeding on ___
insects at night
List 5 characteristics about monotremes
Females lay 1-2 eggs Embryo nourished by yolk inside Hatches very small & partially developed Mother protects & feeds w/mammary glands
Why are modern terrestrial mammals more like Lycaenops than Dimetrodon?
Limbs directly beneath the body
Mammals and dinosaurs appeared around the same time. How long did dino's influence the development of mammals?
150 million years
Difference in mammal & reptile skull?
2 holes in back of the head = reptile 1 hole = mammal
Synapsides gave rise to the mammals. When did they first appear on earth?
300 MYA
How many different species and orders are there of mammals?
4,400 species 20 orders
What is a cow's Rumen & what is its function?
Contains symbiotic bacteria that help break down cellulose
What is the function of the back teeth?
Crushing, grinding, slicing
What are the functions of incisors?
Cutting
When did the dino's go extinct?
End of Cretaceous period 65 MYA
What are the 6 key characteristics of mammals?
Endothermy Hair Completely divided heart Milk Single jaw bone Specialized teeth
What is the function of this organ?
Evaluates input from sensory organs, controls movement, regulates behavior, involved in memory & learning
What are the functions of premolars & molars?
Grind, shear, shred, crush
What are the functions of canines?
Grip, puncture, tear
Explain how a baleen whale eats?
Gulps huge amounts of water --> close its mouth --> pushes water through baleen
What are some of the defining mammalian characteristics that Lycaenops had?
Hair Endothermic Large eyes 4 in long
What structures serve to insulate from that heat loss?
Hair & fat
Most mammals have a thick coat of fur. Which two species do not?
Humans & whales
What function do scientists infer the large sail-like structure had?
Inferred to have blood vessels & was temp. regulator
What are 2 functions of hair for mammals?
Insulation & camouflage
What were 3 characteristics of early mammals as shown by the early mammal Eozostrodon
Large eyes 4 in long Ate insects
What is a Cecum & where is it located in along the GI system?
Large sac branching from small intestine that act as a fermentation chamber