Early Mammal Evolution Quiz

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Questions and Answers

What significant event allowed early mammals to evolve more freely?

  • The rise of reptiles
  • The extinction of the dinosaurs (correct)
  • The Ice Age
  • The development of flight

Morganucodon is the earliest known mammal and appeared around 100 million years ago.

False (B)

What are the two main types of sweat glands discussed, and how do they differ?

Eccrine sweat glands open directly to the skin and help cool the body, while apocrine sweat glands open to hair follicles and have a secondary function in excreting pheromones.

The group of marsupials is called _____, which is known for carrying their young in a pouch.

<p>metharia</p> Signup and view all the answers

Match the types of mammals with their descriptions:

<p>Monotremata = Egg-laying mammals Metharia = Marsupials Eutharia = Placental mammals Morganucodon = Earliest known mammal</p> Signup and view all the answers

Which of the following is a pro of endothermy?

<p>Can support more costly organs (C)</p> Signup and view all the answers

What is the primary function of vibrassae (whiskers) in marine and nocturnal mammals?

<p>Identification of individuals (C)</p> Signup and view all the answers

Hair serves six functions including insulation, protection, and communication.

<p>True (A)</p> Signup and view all the answers

Describe the four growth phases of hair.

<p>Anagen (growth), Catagen (transition), Telegen (resting), Exogen (shedding).</p> Signup and view all the answers

Incisors are used primarily for grabbing and stabbing.

<p>False (B)</p> Signup and view all the answers

Name one distinguishing feature of the cervidae family.

<p>Strong sexual dimorphism</p> Signup and view all the answers

The __________ family is known for having antlers that are almost always male except for caribou.

<p>cervidae</p> Signup and view all the answers

Match the ungulate families with their descriptions:

<p>Bovidae = Blunt rounded nose, horns with permanent bony core Cervidae = Light builds, prominent ears, antlers Antilocapridae = Sometimes called pronghorn antelope, fast land mammals</p> Signup and view all the answers

Which type of teeth are specifically designed for slicing and have a scissor-like function?

<p>Carnassial teeth (A)</p> Signup and view all the answers

Hindgut fermentation occurs primarily in odd-toed ungulates with a complex stomach.

<p>False (B)</p> Signup and view all the answers

What is a distinctive feature of the premolars in herbivores?

<p>Difficult to distinguish from molars</p> Signup and view all the answers

Flashcards

What is Morganucodon?

The earliest known mammal, appearing around 200 million years ago.

What are monotremes?

A group of mammals that lay eggs, with only 5 species globally. They are found exclusively in Australia and New Guinea.

What are the metharia?

A group of mammals characterized by giving birth to altricial young and carrying them in a pouch. Approximately 70% of marsupial species are found in Australia and New Guinea.

What are the eutharia?

A group of mammals that include all placental mammals. They are found on all seven continents and are characterized by nurturing their young within the body through a placenta.

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What is endothermy?

The process of generating heat internally by converting chemical fuel to heat. This allows mammals to maintain a stable body temperature.

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What are eccrine sweat glands?

Sweat glands that open directly onto the skin. In primates, these glands are the primary source of cooling.

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What are apocrine sweat glands?

Sweat glands that open into the base of hair follicles. They are crucial for temperature regulation in non-primates.

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What are mammary glands?

Specialized glands responsible for producing milk. This provides nutrition and antibodies for offspring, fostering dependence on the mother.

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Buoyancy in Mammals

Special adaptations that involve trapping air between the skin and environment, using underfur and guard hairs. This is commonly found in animals like polar bears.

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Protection in Mammals

The use of modified hairs, sebaceous glands, and camouflage to provide protection from predators. This is typical of animals like porcupines and tigers.

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Sensory Adaptations in Mammals

Sensory adaptations like vibrissae (whiskers) help identify individuals and navigate environments, especially in marine or nocturnal mammals.

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Dental Formula

A dental formula is a shorthand way to describe the number of each type of tooth in a mammal's mouth. It uses abbreviations like I (incisors), C (canines), P (premolars), and M (molars).

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Herbivore Teeth

Herbivores lack exaggerated canines, have well-developed incisors for cropping, a diastema (gap between incisors and premolars), and molars that are adapted for grinding plants.

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Carnivore Teeth

Carnivores have well-developed canines and incisors for tearing and killing. Their premolars have high ridges for shearing, and they possess carnassial teeth (modified molars) for slicing meat.

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Omnivore Teeth

Omnivores possess a mix of herbivore and carnivore dental features. They retain canines for display, have premolars with high ridges for shearing, and have larger grinding surfaces on their premolars for processing plant material.

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Carnassial Teeth

Carnassial teeth are specially adapted molars in carnivores that act like scissors. They are located in the back of the jaw and are used for slicing through meat and bone.

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Study Notes

Early Mammal Evolution and Extinction Events

  • Mammals evolved after the Triassic extinction.
  • Dinosaur extinction created opportunities for mammals to diversify.

Earliest Mammal

  • Morganucodon, appearing around 200 million years ago.

Monotremata

  • Egg-laying mammals.
  • 5 species globally.
  • 4 echidnas, 1 platypus.
  • Found only in Australia.

Metatheria (Marsupials)

  • 300 species globally.
  • Mostly found in Australia and New Guinea.
  • Also found in the Americas.
  • Altricial birth (dependent young).
  • Young develop in a pouch.

Eutheria (Placental Mammals)

  • 4,000 species, found on all continents.
  • Young develop inside the mother's body via a placenta.
  • Offspring can be altricial or precocial (more developed at birth).

Endothermy

  • Internal heat production, converting chemical energy to heat.
  • Pros: Maintain optimal body temperature, support complex organs.
  • Cons: Higher metabolic demands.
  • Ecological Influence: Allowed colonization of diverse environments; hair and shivering for insulation and thermoregulation.

Sweat Glands

  • Eccrine: Opens directly to skin; primary cooling mechanism in primates, less common in other mammals. Found on palms and soles of non-primates.
  • Apocrine: Opens to hair follicles; more important for non-primates; secondary function of secreting pheromones.

Mammary Glands

  • Produce milk for offspring nourishment.
  • Provides nutrition and antibodies.
  • Creates offspring dependence.
  • Located in females' breasts.

Neocortex

  • Region of the brain responsible for higher-level cognitive functions: sensory perception, spatial reasoning, language.
  • Link to endothermy: Endothermy and neocortex development may be linked.
  • Human Brain: Approximately 75% of the human brain is the neocortex.

Hair

  • Keratin-based structures.
  • Follicle stem cells generate hair.
  • Growth Phases: Anagen (growth), Catagen (transition), Telegen (resting), Exogen (shedding).

Teeth Functions

  • Evolved from reptilian structures.
  • Diverse functions: grinding, stabbing, slicing, digging, chiseling, lifting.

Non-Physiological Thermoregulation

  • Panting.
  • Covering in water (water buffalo).
  • Large ears (certain hares).

Hair Functions

  • Insulation: Traps air, underfur and guard hairs—common in polar bears.
  • Buoyancy: Trapped air for floating—sebaceous glands—common in otters.
  • Protection: Sebaceous glands, modified hairs, camouflage—common in porcupines and tigers.
  • Sensory: Vibrassae (whiskers)—common in nocturnal/aquatic mammals—individual recognition.
  • Locomotion: Gliders use for flight
  • Communication: Display/intimidation, aposematic coloration (warning signals), indicating toxicity/unpalatability—skunks.

Tooth Types

  • Incisors: Front teeth, single-rooted, nipping, strong vertically.
  • Canines: Single pair per jaw side, strong in all directions, grabbing/stabbing, sexual display.
  • Premolars: Anterior cheek teeth, multiple, highly variable, species-dependent.
  • Molars: Posterior cheek teeth, often larger than premolars, more cusps than premolars.

Dental Formula

  • ICPM: Numbering system used to represent top and bottom teeth.

Herbivore Teeth

  • No exaggerated canines.
  • Well-developed incisors.
  • Diastema (gap between incisors and canines).
  • Difficult to distinguish premolars from molars.

Carnivore Teeth

  • Well-developed canines and incisors.
  • Premolars demonstrate high ridges.
  • Carnassial teeth (modified molars); for slicing.

Omnivore Teeth

  • Retains canines for display.
  • Premolars with high ridges for grinding.
  • Premolars with grinding surfaces similar to herbivores

Carnassial Teeth

  • Slicing teeth, scissor-like, self-sharpening.

BC Ungulates

  • Bovidae:
    • Blunt/rounded nose, sometimes sexually dimorphic; horns (permanent bony core, keratin sheath); bighorn sheep, mountain goats.
  • Cervidae:
    • Lighter builds, prominent ears, strong sexual dimorphism; antlers (male except caribou).
    • Moose, elk, mule deer, white tailed deer, caribou
  • Antilocapridae:
    • Pronghorn, extirpated BC sagebrush habitats; one of the fastest land mammals.

Hindgut Fermentation

  • Odd-toed ungulates (e.g., horses).
  • Simple stomach.
  • Large intestine and caecum are main sites of fermentation.

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