Mammals (21,22)

Question 1

What are the three major groups of amniotes, and how are they distinguished?

Answer 1

Synapsids, Anapsids, and Diapsids; distinguished by the structure of the skull roof

Question 2

What is the significance of cynodonts in mammalian evolution?

Answer 2

Cynodonts showed features
- heterodont teeth
- secondary palate
- diaphragm; supporting a higher metabolic rate

Question 3

How did the jaw articulation evolve in mammals?

Answer 3

Early synapsids had a quadrate-articular jaw articulation, which evolved into the dentary-squamosal articulation in mammals, with the quadrate and articular bones becoming the incus and malleus.

Question 4

Name three major characteristics of modern mammals.

Answer 4

Hair, mammary glands, and endothermy.

Question 5

What are the two clades of living mammals?

Answer 5

Monotremes and Therians (which include Metatherians and Eutherians).

Question 6

What is unique about monotreme reproduction?

Answer 6

They are oviparous and lay eggs.

Question 7

What are the two types of hair in mammals, and their functions?

Answer 7

Guard hairs (protection and coloration) and underhairs (insulation)

Question 8

What are true horns, and how do they differ from antlers?

Answer 8

True horns are hollow keratin sheaths over bone, found in both sexes, and grow continuously. Antlers are solid bone, shed annually, and typically found only in males.

Question 9

What type of dentition do mammals have, and how does it differ from reptiles?

Answer 9

Mammals have heterodont dentition (differentiated teeth), whereas reptiles have homodont dentition (uniform teeth)

Question 10

How do ruminant herbivores digest cellulose?

Answer 10

Through a four-chambered stomach and microorganisms in the rumen.

Question 11

What feature allows mammals to separate nasal and oral cavities for efficient gas exchange?

Answer 11

A secondary palate.

Question 12

Describe the pathway of air through the mammalian respiratory system.

Answer 12

Nostrils → Nasal chamber → Pharynx → Glottis → Larynx → Trachea → Bronchi → Bronchioles → Alveoli

Question 13

What are the four types of estrous cycles in mammals?

Answer 13

Monestrous, diestrous, polyestrous, and menstrual cycles.

Question 14

How do marsupial placentas differ from those of eutherians?

Answer 14

Marsupials have a choriovitelline placenta, while eutherians have a chorioallantoic placenta

Question 15

Compare the adaptations in teeth and digestive systems between carnivorous, herbivorous, and omnivorous mammals.

Answer 15

Carnivores have sharp canines and bladelike molars for tearing flesh and a short digestive tract. Herbivores have broad molars for grinding, reduced canines, and long digestive tracts with fermentation chambers for cellulose digestion. Omnivores have versatile dentition, including broad molars for crushing, and moderately developed digestive systems.

Question 16

Explain the evolutionary advantages of mammalian viviparity and its associated energy trade-offs.

Answer 16

Viviparity allows females to move and access resources during gestation, providing better survival for offspring. However, it requires high energy expenditure during gestation and postnatal care, increasing parental investment.

Question 17

How did the evolution of mammalian hair contribute to their success in diverse environments?

Answer 17

Hair provided insulation, enabling mammals to maintain body heat in cold environments (endothermy). Modified hairs like vibrissae (whiskers) enhanced sensory functions, and spines provided defense.

Question 18

Discuss the significance of the evolution of mammary glands in mammals.

Answer 18

Mammary glands allowed mammals to nourish their young with nutrient-rich milk, reducing dependence on environmental food sources and enabling survival in varied habitats. This adaptation likely enhanced reproductive success and offspring survival rates.

Question 19

Contrast monotreme reproduction with that of eutherian mammals in terms of offspring development and maternal investment.

Answer 19

Monotremes lay eggs, providing less maternal investment pre-hatching, and the young are highly altricial. Eutherians nourish embryos via the placenta, leading to more developed offspring at birth and higher maternal energy investment during gestation.

Question 20

Amniotes

Answer 20

A group of tetrapods
- presence of an amniotic egg
(which includes reptiles, birds, and mammals)

Question 21

Synapsids

Answer 21

One of the three major groups of amniotes
- single temporal fenestra in the skull

Question 22

Pelycosaurs

Answer 22

Early synapsids that were herbivores and carnivores in the Permian period; not closely related to modern reptiles

Question 23

Therapsids

Answer 23

Advanced synapsids that evolved from pelycosaurs, showing more efficient locomotion and feeding adaptations

Question 24

Cynodonts

Answer 24

A subgroup of therapsids with traits like heterodont teeth, secondary palate, and a diaphragm, indicating higher metabolic rates

Question 25

Diphyodont

Answer 25

Having two sets of teeth in a lifetime – deciduous (“baby teeth”) and permanent teeth, as seen in most mammals

Question 26

Polyphyodont

Answer 26

Having continuous tooth replacement throughout life, a characteristic of ancestral amniotes

Question 27

Dentary-Squamosal Articulation

Answer 27

A jaw joint found in mammals where the dentary bone of the lower jaw articulates with the squamosal bone of the skull

Question 28

Incus, Malleus, Stapes

Answer 28

The three bones of the mammalian middle ear, evolved from the jawbones of early synapsids, facilitating acute hearing

Question 29

Endothermy

Answer 29

ability to maintain a stable internal body temperature through metabolic heat production

Question 30

Hair (Pelage)

Answer 30

A defining characteristic of mammals, providing insulation and sometimes modified for sensory or defensive purposes (e.g., whiskers, spines)

Question 31

Guard Hairs

Answer 31

Coarse and long hairs that protect against wear and provide coloration

Question 32

Heterodont Dentition

Answer 32

A condition where teeth are differentiated into various types (e.g., incisors, canines, premolars, molars) for specialized functions

Question 33

Monotremes

Answer 33

Egg-laying mammals, such as the platypus and echidnas, found in Australia and New Guinea

Question 34

Marsupials

Answer 34

Mammals that give birth to underdeveloped young that complete their development in a pouch (marsupium)

Question 35

Eutherians

Answer 35

Placental mammals with a chorioallantoic placenta, allowing extended gestation and advanced offspring development

Question 36

Choriovitelline Placenta

Answer 36

A transient placenta found in marsupials, formed by the yolk sac and chorion

Question 37

Chorioallantoic Placenta

Answer 37

The placenta of eutherians, formed by the fusion of the chorion and allantois, facilitating nutrient exchange and waste removal

Question 38

Viviparity

Answer 38

Giving birth to live young, with the embryo developing within the mother’s uterus

Question 39

Estrus Cycle

Answer 39

The reproductive cycle in most female mammals during which they are fertile and receptive to mating

Question 40

Arrector Pili Muscles

Answer 40

Small muscles attached to hair follicles that make the hair stand upright, aiding in insulation

Question 41

Ruminant Herbivores

Answer 41

Herbivores with a four-chambered stomach for fermenting plant material, including the rumen, reticulum, omasum, and abomasum.

Question 42

Coprophagy

Answer 42

The re-ingestion of feces to extract additional nutrients, common in some rodents and lagomorphs.

Question 43

What makes mammalian integument distinct from other vertebrates?

Answer 43

Mammalian integument is thicker and more complex, adapted for terrestrial life with structures like hair and glands.

Question 44

What keratinized structures are found in mammals?

Answer 44

Hair, hooves, claws, and nails.

Question 45

What is the typical body temperature range in mammals?

Answer 45

36–38°C.

Question 46

Name two adaptations mammals have for cold environments

Answer 46

Increased fur thickness and hibernation.

Question 47

How does fur thickness change in cold environments?

Answer 47

Fur thickness can increase by up to 50%, with underhair acting as the primary insulating layer.

Question 48

What type of heart do mammals have, and how does it differ from fish and amphibians?

Answer 48

Mammals have a four-chambered heart, while fish have a two-chambered heart and amphibians/reptiles have three chambers.

Question 49

What is the primary mechanism mammals use for ventilation?

Answer 49

Negative pressure ventilation.

Question 50

Which muscles are involved in negative pressure ventilation?

Answer 50

The diaphragm and intercostal muscles.

Question 51

What are the four types of mammalian teeth, and their functions?

Answer 51

Incisors: Biting, cutting, and stripping.
Canines: Seizing, piercing, and tearing.
Premolars and Molars: Grinding and crushing

Question 52

What are the five functional regions of the mammalian alimentary canal?

Answer 52

Reception, conduction and storage, grinding and early digestion, terminal digestion and absorption, and water absorption/concentration of solids.

Question 53

Name the four trophic categories of mammals based on feeding specialization.

Answer 53

Insectivores, carnivores, omnivores, and herbivores.

Question 54

How has the vertebrate brain evolved in mammals?

Answer 54

It has increased in complexity, with deep fissures and intricate structures, culminating in the mammalian brain.

Question 55

What are two key sensory receptors in mammals and their functions?

Answer 55

Chemoreceptors: Detect chemicals in the environment.
Mechanoreceptors: Detect touch and sound.

Question 56

What are the three reproductive strategies in vertebrates?

Answer 56

Oviparous: Egg-laying.
Ovoviviparous: Internal egg development with nourishment from yolk.
Viviparous: Live birth with direct nourishment from the mother.

Question 57

What is unique about the reproductive strategy of monotremes?

Answer 57

They are oviparous mammals that lay eggs.

Question 58

How does lactation benefit mammalian young?

Answer 58

It provides a nutrient-rich food source, allowing young to rely on their mothers rather than foraging.

Question 59

Explain the process and benefits of negative pressure ventilation in mammals compared to positive pressure ventilation in amphibians.

Answer 59

Negative pressure ventilation in mammals involves expanding the thoracic cavity using the diaphragm and intercostal muscles, creating a pressure gradient that draws air into the lungs. This system is more efficient, allowing mammals to take in larger volumes of oxygen compared to the forceful air intake used by amphibians in positive pressure ventilation.

Question 60

Compare the reproductive adaptations in monotremes, marsupials, and eutherians, and discuss how these adaptations support their survival.

Answer 60

Monotremes lay eggs, minimizing maternal investment pre-hatching.
Marsupials give birth to underdeveloped young that complete development in the pouch, enabling shorter gestation and faster reproduction.
Eutherians use a chorioallantoic placenta for extended gestation, allowing young to be born more developed, increasing survival rates.

Question 61

How do teeth and digestive systems differ among insectivores, herbivores, carnivores, and omnivores?

Answer 61

Insectivores: Pointed teeth for puncturing, short digestive tracts.
Herbivores: Broad molars for grinding cellulose, long alimentary canals, and fermentation chambers.
Carnivores: Sharp canines and short digestive tracts for digesting meat.
Omnivores: Versatile dentition for processing both plant and animal materials, moderately developed digestive systems.