week 21

Question 1

The mammalian skull is formed of many ____

Answer 1

bones, most of which are fused along suture lines to produce the overall shape of the skull.

Question 2

The structure and shape of the skull and teeth of an animal can suggest

Answer 2

a lot about the ecology and lifestyle of that animal.
Different structures will be adapted for different functions. When you look at the different skulls think about how the structure relates to function, and what this can tell you about the animal’s ecology.
What is the benefit of having eye sockets on the side of the skull?
Why do some animals have very large canines?
What do large eye sockets relative to the skull suggest about the lifestyle of an animal?

Question 3

Mammals display a wide variety of tooth shapes and sizes.

Why is this important?

Answer 3

This diversity of teeth is interesting to examine because it can tell us something about an animal’s diet and lifestyle.

Question 4

There are 4 main types of teeth in mammals:

Answer 4

incisors, canines, premolars, and molars.

Question 5

What is a dental formula?

Answer 5

can be used to describe the number and types of teeth that an animal has.

Question 6

Give an example of a dental formula?

Answer 6

The dog skull shown below has a dental formula of I3/3, C1/1, P4/4, M2/3 = 42.
The formula is written using the first letter of the tooth type (I, C, P, and M) followed by how many are on each side of the upper and lower jaws, e.g. M2/3 means, on each side, 2 molars in the upper jaw and 3 molars in the lower jaw.
The final number is the total number of teeth, e.g. ( 3+3 + 1+1 + 4+4 + 2+3 ) x 2 sides = 42 total teeth.

Question 7

The carnassial teeth are adapted for

Answer 7

shearing, and have developed from a premolar in the upper jaw and a molar in the lower jaw.

Question 8

Examine the image of a skull. Which features suggest that this mammal is more likely a prey animal rather than a predator?

Answer 8

The features of mammal skulls, such as position of eyes, type of teeth, shape of head, can give us clues as to the lifestyle and diet of an animal.

Flat, grinding teeth
Large eye sockets either side of head

Question 9

What is the dental formula for dogs (Canis lupus)?

Answer 9

I3/3, C1/1, P4/4, M2/3

Question 10

In the practical you will answer questions on mammal skull evolution.

Which of the following are mammal taxonomic groups?

Answer 10

Chiroptera
Xenarthra
Hyracoidea
Cetacea
Lagomorpha

Question 11

How are pinnipeds adapted?

Answer 11

Pinnipeds – a term meaning feather/fin/web-footed’

Pinnipeds are adapted for both life on land and in water.

Question 12

Why do pinnipeds have big lenses?

Answer 12

to be able to focus on objects properly underwater

Question 13

Why do pinnipeds have adaptable irises?

Answer 13

to limit the amount of light entering their eyes and prevent damage to their retina but also prevent them being too short-sighted.

Question 14

Why do pinnipeds have a tapetum lucidum?

Answer 14

Can get dark in the deep waters and so like cats and many other nocturnal mammals they have a structure known as a tapetum lucidum, which is like a mirror behind the retina to reflect light back across the light sensitive cells of the retina and therefore has a second chance at being detected by the photoreceptors.

Question 15

Name some basic attributes of eared seals?

Answer 15

• Fur seals (9) and sea lions (7).
• Large fore-flippers for propulsion.
• Hind-flippers play no part in sustained swimming.
• More agile than seals on land.
• Can support weight on fore flippers, both fore- and hind-flippers used in terrestrial locomotion.

Question 16

What are the benefits of a waterproof coat overlying a thick, woolly underlayer for fur seals?

Answer 16

which is used to trap warm air for effective insulation when underwater

Question 17

Why are eared seals more agile on land?

Answer 17

Also much more agile on land as their powerful forelimbs can support their body unlike seals which just flomph.

Question 18

Compare movement on land between true seals and eared seals.

Answer 18

Here’s a eared sale, you can see it’s supporting itself on those fore flippers whereas this true seal like this grey seal is belly flopping along the mud.

Question 19

Name the basic properties of true seals.

Answer 19

• Use hind flippers for swimming
• Main muscle mass at rear
• Not agile on land
• Common and grey seals breed in UK.

Question 20

Name some basic properties of seals.

Answer 20

Produce click vocalisations under water- may be used in echolocation
Delayed implantation
Limited mother-pup contact

Question 21

Why is delayed implantation in females a good strategy?

Answer 21

It’s a good strategy as it reduces the time that seals need to spend on land, compressing birth and mating into a single period during spring or early summer.

Question 22

Why do males arrive a few days or weeks before females in the breeding season?

Answer 22

take up territories.

Question 23

What happens after the female seals have given birth?

Answer 23

Females then come ashore and before birth shortly after. Each mothers then suckles her infants over a few days (as in hooded seals), or several weeks (as in ringed seals) before coming back into estrus and mates with the nearest dominant bull. Thus mother-pup contact can be pretty limited in true-seal species.

Question 24

Why do female seals delay implementation?

Answer 24

They also show an interesting behaviour called delayed implementation, so the females delay implantation of the embryo by up to about four months. The reason for doing this, is that they can mate and give birth in one period when they are ashore on land.

Question 25

Outline the properties of Elephant seal social organisation.

Answer 25

• Highly polygynous (resource defence). Males 3x mass of females, huge proboscis. No paternal care after mating.
• Undertake bloody fights for dominant position on mating beaches.
• Few males monopolise.
• Alpha male may inseminate 100 females/season.
• Females may produce up to 14 pups in 12y lifespan.

Human males: 200-500 million sperm/ejaculate.

Question 26

Why is there a difference in sexual maturity in male and female seals?

Answer 26

Females reach sexual maturity at 2-3 years but males aren’t ready until 6-7 years old and probably won’t mate successfully until they are 9-10 as they need to invest a lot of energy into getting big and strong before they can compete for alpha status.

Question 27

What is polygynous and what does it promote?

Answer 27

so you get one male mating with several females and it’s sort of polygyny that we call resource defense polygyny. So the females are dominating a resource in this case a patch of beach that the females need for giving birth and defending it.

Question 28

What are some other behavioral tendencies in elephant seals?

Answer 28

• Peripheral, subdominant males hang around edges of harems and intercept females as they return to sea.
• Bulls are so aggressive they attempt to mate with pregnant females, or may trample pups.
• Male pups attempt to steal milk from females which aren’t their mothers, so they may grow to be big – not seen in females.

Question 29

What are some basic properties of the Order Sirenia?

Answer 29

• Only marine mammals feed primarily on plants.
• Stomachs not compartmentalised, long intestines (45 m in manatees).
• Between small and large intestines is a large mid-gut caecum where cellulose digestion occurs.
• Can process 8-15% of body mass in low quality plant material daily.
• Expend little energy – 1/3 that expected for mammals of their size
• Move slowly, live in warm tropical waters.
• Constant replacement of teeth, as in elephants, allows them to eat plants that contain much abrasive silica.
• Store a lot of fat. Amazonian manatees can fast for 6 months in the dry season, when plants are scarce.

Question 30

What takes place in the large midgut cecum in the sirenians?

Answer 30

. Here cellulose is digested by bacteria and this system allows sirenians to process some 8-15% of their body weight’s worth of poor quality plant material into enough energy and nutrients to meet their daily requirements. When you consider some manatees weigh as much as 1,600kg that’s no mean feat!

Question 31

How to the manatees expend as little energy as possible?

Answer 31

A typical mammal of the same weight would be expected to expend three times as much energy. Their energy expenditure is further reduced by residing in tropical waters which are lovely and warm and so relatively small quantities of energy are burnt keeping themselves warm. Manatees in the Atlantic generally avoid areas where temperature drop below 20C.

Question 32

How do the manatees save energy?

Answer 32

They have adaptations that allow them to save energy, for their body size they’re expanding only about a third of the energy that you would predict, given their body mass and they do this, partly by moving very, very slowly, partly by living in warm waters with the costs of thermal regulation relatively low.

Question 33

Why do the manatees replace their teeth?

Answer 33

They have a constant replacement of teeth, as we see also in elephants, and you’ll see this in the practical class.
And this is necessary as the teeth of abrade very, very quickly from the silica in plant material they’re very fat and they can live off this fat for long periods of time, so in the Amazon the manatees there can actually fast for six months or so in the dry season when there’s a shortage of plant food available.

Question 34

What are some differences between the manatees and the dugong?

Answer 34

Unlike manatees which spend at least some of their time in freshwater, the dugong is entirely marine where they search the sea bed for carbohydrate rich rhizomes and browse terminal leaves of certain seagrass species.
So here are manatees and dugongs, there are three species of manatees, one species of dugong, there is also this extinct Steller’s sea cow that measured up to a seven and a half meters in length way up to six tons. One of the threats to manatees nowadays, you can see, the distribution of them in little insert map comes from boat propellers and they tend to get hit by boat propellers than this can damage their around integument.

Question 35

What are species are found in the toothed whales?

Answer 35

dolphins, porpoises, belugas, narwhals, sperm whales, pygmy sperm whales and beaked whales.

Question 36

What species are found in the Baleen whales?

Answer 36

gray whale, rorquals (blue, minke, humpback, fin whale etc), right whales and pygmy right whales.

Question 37

What have palaeontologists found out about whales and dolphins?

Answer 37

Animals illustrated here are only a fraction of the dozens of species of fossil whales that palaeontologists have discovered in recent decades.
By studying fossils, palaeontologists have been able to show how traits found in living whales evolved gradually, not all at once.
Started off in freshwater then as moved into salt water also evolved shorter legs and longer tail.
Some point around 40 mya tail fluke evolved then hind limbs lost completely although vestiges of bones still seen internally.
Only after the split of odontocetes and mysticetes that echolocation evolved in the former and baleen in the latter.

Question 38

What are the basic features of the blue whale?

Answer 38

• May reach 27m, weigh 150 tonnes (33 elephants).
• Only possible in water.
• Streamlined. Lost hind limbs (trace internally). No external ears. Horizontal fins, boneless tail fluke. Some spp have an upright boneless dorsal fin.

Question 39

What are the basic features of baleen whales?

Answer 39

• Largest whales.
• Paired nostrils separate – blowhole double.
• Baleen plates (series of horny plates – sides of upper jaw instead of teeth).

Question 40

What varies in relation to the size and species of baleen whales?

Answer 40

“the thickness and number of baleen plates is related to the size and species of the prey taken. Thus a gray whale, a highly selective benthic feeder, has a shorter, stiffer baleen and fewer throat grooves (usually 2-3) than the rorquals (with 14-100), and is thereby adapted for scouring the seabed. In rorquals the baleen is longer and wider. In the blue whale, the plates may reach a width of nearly 0.75m; in other rorquals they are considerably narrower, and this dictates the diet of each. In the right and bowhead whales the baleen is extremely long and fine and these whales feed on the smallest planktonic invertebrates of any of the baleen whales.”MD

Question 41

What is present in a cetaceans countercurrent system?

Answer 41

In these systems arteries are closely surrounded by veins so that cold blood in the veins of these appendages on its way back to the heart gets warmed by the arterial blood coming from the body. Very effective way to prevent heat loss and therefore minimise energy expenditure. Similar systems are now employed in energy efficient houses to keep internal rooms warm while removing stale air and replacing it with fresh air from outside.

Question 42

What are the basic properties of toothed whales?

Answer 42

• Jaws extend as beak-like snout.
• Behind snout forehead rises in rounded curve - the melon.
• Possess single nostril single blowhole.

Question 43

What species are found in the toothed whales?

Answer 43

Group includes dolphins, river dolphins, porpoises (spectacles porpoise in picture), beluga and narwhal (pic), sperm whale, pygmy sperm whale and beaked whales.

Question 44

What does reproductive conflict increase in orcas?

Answer 44

Reproductive conflict with younger generation daughters increases mortality risk for calves of older mothers.

So post reproductive females, are very important for the social group in finding scarce fish resources. So there are benefits to the daughters benefits to granddaughters but there’s also reproductive conflict between older generation mothers and their offspring.

So when an older generation mother and a younger generation female in the same group breed at the same time, and only when they breed at the same time.
The mortality rate of calves is much higher for those born to older generation females compared to the risks to calves from younger generation females.
So there’s a conflict ,a reproductive conflict, between older generation mothers and younger generation mothers. And so the increased risk of mortality, to the offspring of older generation mothers, is another factor that results in them, giving up reproduction, very often when they’re perhaps about 40 years old.

Question 45

What are the costs and benefits to daughter and granddaughter orcas?

Answer 45

So we’ve got benefits in terms of benefits to daughters and granddaughters and costs in terms of costs of mothers in reduced reproductive success in these groups. And it’s amazing if you watch drone footage of these orcas feeding in the wild you can see mothers catching food breaking bits off the food and feeding it to kin in their group, and this has only recently been seen by the use of drones.

Question 46

What are the properties of tooth whaled echolocation?

Answer 46

Another interesting adaptation of the toothed whales is echolocation. So echolocation occurs and things like bats. it also occurs in certain species of swiftlets and oilbirds.
And echolocation evolves in habitats where vision is pretty useless. So night time for bats, for instance. Caves for cave swiftlets and underwater turbid habitats. So light travels not very far underwater.
Sound travels extremely effectively in water compared within the air.
And echolocation has evolved in at least 13 species of toothed whales. Typically these toothed whales use clicks. These clicks can be short around about a millisecond in length.
And they tend to be largely ultrasonic, very high frequencies sometimes going up to 220 kilohertz. We can hear sound up to about 20 kilohertz, so this is way above the frequencies that we can hear.

Question 47

What are the differences between bat echolocation and whale echolocation?

Answer 47

The process of echolocation in whales and dolphins is very different from that in bats. Bats produce sound in their larynx in the same way we produce speech.
Toothed whales produce sound in the nasal passages in things called monkey lips.
They then use this melon, sort of domed waxy lens-shaped body on the forehead. And this focuses sound out into the water.
Sound returns through oil filled sinuses in the lower jaw to reach the inner ear. And the ear is isolated from the skull by bubbly foam.
So it’s quite a different process from the ones that we see in bats.
But it still involves the use of echolocation.

Question 48

How do sperm whales echolocate?

Answer 48

• Sperm whale produces intense ultrasound.
• May stun prey such as squid.
• Several fish evolved sensitivity to ultrasound – whale detectors?

Question 49

Outline the basics of long-distance communication in whales?

Answer 49

• Large baleen whales use low frequencies (20-3000 Hz).
• Low frequencies travel far.
• Deep ocean channels form under specific water densities, temperature and currents, and may trap sound like a cylinder.
• Sound may travel 5600 km in such channels.
• Sound pollution (boat noise).

Question 50

Humpback whale songs change ______.

Answer 50

annually

Question 51

What is the melon?

Answer 51

(waxy, lens-shaped body)

Melon is a waxy, lens-shaped body in the forehead which focuses sounds produced in the nasal passages.

Question 52

Although produced in a different way, what are whale/dolphin echolocation convergent to?

Answer 52

Although produced in a different way this echolocation is convergent with the chiropterans/the bats which we’ll be looking at tomorrow.

Question 53

What are the inner ears of dolphins surrounded by and why?

Answer 53

which is surrounded by material analogous to bubble wrap to detect returning sound pulses without interference from other resonances.

Question 54

What are the threats to underwater communication?

Answer 54

one of the threats to acoustic communication and the water by the cetaceans, comes from sound pollution, especially the noises of boats etc. There’s also evidence, quite good evidence, that sounds from naval tests, naval sonar, has also affected cetaceans and could have contributed to some of the mass strandings that have been seen around the world.

Question 55

Why do whale songs change?

Answer 55

There are also dialects between different populations of whales.
So those orcas, for instance, that I showed you earlier, that was studied in the study of menopause off British Columbia and off the west coast of the northern US as well, you get a northern group in a southern group, and they have slightly different dialects in their voices.

So these sounds seem to be culturally transmitted within populations and they can change and be learned from generation to generation.

Question 56

What happens during the breeding season in humpback whales?

Answer 56

“During the breeding season lone males repeat long, complex songs, each lasting for about 10 minutes, in unbroken series. They can sing incessantly for more than 24 hours. Analysis of these songs reveals that the sound sequences of which they are composed are generated by a hierarchical model. Each song consists of a series of themes repeated in a specific order; the themes in turn are made up of phrases repeated a variable number of times. Most males within a single population perform very similar songs. However, the song changes gradually but continuously over time, so that songs from different years are quite distinct from one another, and there are no common sounds in songs recorded a decade apart… humpback males learn the detailed acoustic structure of their songs, and that whales from different populations do not sing different songs because of different genotypes, but rather because they imitate what they hear. In other words , humpback song is a form of culture.”MD
West coast humpbacks migrate into the east coast population in Australia and the resident east coast members started copying their song and eclipsed their own in just two years.

Question 57

Humans belong to the mammalian order

Answer 57

Blank 1: primates

Question 58

A bat wing is modification of the

Answer 58

pentadactyl limb.

Question 59

Bats are the only mammals capable of

Answer 59

powered flight.

Question 60

Wing-shape determines

Answer 60

flight speed and manoeuvrability.
Wing loading (weight to wing area ratio).
Notule can reach speeds of at least 50km/h
They also have a very high wing loading, what this means is that they’re carrying a lot of weight per unit wing area.
And the high wing loading results in them having fast flight but low maneuverability, this means that they feed in habitats where fast flight is possible in open spaces and in areas where they don’t need to be maneuverable again open spaces. So high wing loading small wings relative to body mass.
High aspect ratio, which is is a measure of how long and pointy the wing actually is. These are features that allow these bats to fly rapidly but with low maneuverability in open spaces.

• Conversely species that fly in forests and confined spaces have a low aspect ratio and a low wing loading.
• Low loading confers slow flight, and the ability to turn in small volumes of space.

Question 61

•High frequencies used in echolocation have ____wavelengths, allowing detection of small objects.

Answer 61

short

Question 62

• Of course eating insects means that they provide important ecosystem services eating so-called ____ species.
• Have ____ stomachs to store prey as an adaptation to the ___ period of high availability of prey in the night.
• _____ intestine permits a ____ digestion and hence low flight weight.

Answer 62

‘pest’

large
short

Short
rapid