Week 20 - Evolution and Diversity of Mammals Part 2

What are the 3 families of Pinnipedes?

• Walrus - Odobenidae

• Eared seals - Otariidae

• True seals - Phocidae

Dont need to remember the names of the families.

What are the visual adaptations of Pinnipedes?

• Have large irises, for low light in water

• Have a capetum (a reflective layer behind the retina), which caauses light to bounce back, giving the retina a second chance to absorb more photons of light.

• Have very active tear glands to lubricate them against the salt water.

Where do Pinnipedes feed and breed?

Feed offshore, give birth on land.

In walruses (a type of Pinnipede), which genders have tusks?

Both genders have tusks.

In walruses (a type of Pinnipede), what are tusks used for?

In males: male-male competition

In general: defence or movement (they can be used to pull themselves up onto land).

How can eared seals (a type of Pinnipede) be ditinguished from true seals (a type of Pinnipede)?

They have an external ear, a pinna.

What are fur seals and sea lions classified as?

Eared seals (a type of Pinnipede).

Which limbs of the eared seals (a type of Pinnipede) act in propulsion?

Large fore-flippers.

Which are more agile, eared seals or seals on land (both are types of Pinnipede)?

Eared seals.

Which limbs do eared seals (a type of Pinnipede) use in terrestrial locomotion?

Both fore and hind flippers are used in terrestrial locomotion.

What do true seals (a type of Pinnipede) use for swimming?

Hind flippers.

Where is the main muscle mass of true seals (a type of Pinnipede) found?

Found at the rear.

Which 2 true seals (a type of Pinnipede) breed in the UK?

The common seal

The grey seal.

How do seals use sound underwater?

They produce clicks, possibly for echolocation.

What is delayed implantation in seals? Why is this useful?

The embryo does not implant immediately after fertilisation, allowing development to be timed so mothers can spend less time on land and give birth under optimal conditions.

What is notable about seal mother–pup interaction?

Contact is relatively limited.

Why is seal milk highly fatty and energy-rich?

It is extremely high in fat to provide maximum energy, allowing pups to grow quickly and reduce the time spent on land.

What type of mating system do elephant seals have?

They are highly polygynous (have multiple mates) with resource defence mating.

What is a proboscis (found in male elephant seals)?

A proboscis is an elongated, flexible appendage or tube located on the head of an animal, acting as a nose, snout, or feeding organ.

How do male elephant seals differ from females?

Males are about 3× larger, have a large proboscis, and provide no paternal care.

How do dominant male elephant seals gain mating success?

Through bloody fights for dominance on breeding beaches.

How many females can an alpha male inseminate in a season?

Up to about 100 females per breeding season.

What is the reproductive output of female elephant seals?

Up to 14 pups over a ~12-year lifespan.

What do subdominant male elephant seals do?

They stay at the edges of harems and try to intercept females returning to sea.

What extreme behaviours do male elephant seals show?

They may attempt to mate with pregnant females or trample pups.

What is unusual about male elephant seal pup behaviour?

Male pups may steal milk from unrelated females, contributing to larger adult size (not seen in females).

What distinguishes order Sirenia?

They are the only marine mammals to feed primarily on plants.

How is the Sirenia digestive system adapted for plant digestion?

They have long intestines and a large mid-gut caecum for cellulose digestion.

How much food can sirenians process daily?

About 8–15% of their body mass in plant material.

What lifestyle supports low energy use in sirenians?

Slow movement and living in warm tropical waters.

How do sirenians deal with abrasive plant material?

They have continuously replacing teeth, similar to elephants.

How do sirenians survive periods of low food availability?

They store fat; Amazonian manatees can fast for up to 6 months.

Which organisms make up the order Cetartiodactyla?

Whales and Dolphins

What are the closest living relatives to the Cetartiodactyla?

Closest living relatives are Artiodactyls.

What are the two suborders of whales and how many species do they include?

Baleen whales (Mysticeti, 10 species) and toothed whales (Odontoceti, 67 species).

How do baleen whales feed?

They use baleen plates to filter plankton and small invertebrates from seawater.

How do toothed whales feed?

They use teeth to catch and eat fish and squid.

What body shape adaptation do blue whales have?

A streamlined body to reduce drag in water.

What has happened to the hind limbs of blue whales?

They are lost externally but remain as internal vestigial structures.

Do blue whales have external ears?

No, they lack external ears to reduce water resistance.

What is the function of the blue whale tail fluke?

A horizontal, boneless fluke used for propulsion.

What is the function of the dorsal fin in some whale species?

A boneless vertical fin used for stability while swimming.

What is a key feature of baleen whales in terms of size?

They include the largest whales on Earth.

How are the nostrils of baleen whales arranged?

They are paired and form a double blowhole.

What are baleen plates?

Horny (keratin) plates in the upper jaw used for filter feeding instead of teeth.

What is a key feature of toothed whale jaws?

They are extended into a beak-like snout.

What is the melon in toothed whales?

A rounded structure in the forehead used in sound production and echolocation.

How many blowholes do toothed whales have?

One (a single blowhole formed from one nostril).

Why do toothed whales use echolocation?

Because light is limited underwater and sound travels far, making echolocation effective for hunting and navigation.

What is the frequency and duration of toothed whale echolocation clicks?

Very short clicks (<1 ms) ranging from about 0.25–220 kHz.

Where is sound produced in toothed whales?

In the nasal passages using “monkey lips”.

What is the function of the melon in echolocation?

It focuses and directs sound waves.

How do toothed whales receive echolocation echoes?

Through oil-filled sinuses in the lower jaw that transmit sound to the inner ear.

How is the inner ear adapted for echolocation?

It is isolated from the skull by a foam-like structure to improve sound detection.

What is special about sperm whale echolocation?

It produces intense ultrasound that may stun prey like squid.

What evolutionary response have some fish developed?

Sensitivity to ultrasound, possibly to detect approaching whales.

What type of sound do baleen whales use for long-distance communication?

Low-frequency sounds (about 20–3000 Hz).

Why do low-frequency whale calls travel so far?

Low-frequency sounds propagate further in water with less energy loss.

What are deep sound channels in the ocean?

Layers of water that trap and guide sound due to temperature, salinity, and pressure differences.

How far can whale calls travel in deep sound channels?

Up to about 5600 km.

What is a modern threat to whale acoustic communication?

Ocean sound pollution from human activity.

What is the Order Chiroptera? How many species are in this order?

A mammalian order consisting of bats, with over 1,100 described species.

How were bats traditionally classified?

Into two suborders: Megachiroptera and Microchiroptera.

What are Megachiroptera commonly known as?

Which family do Megachiroptera belong to?

Where are Megachiroptera generally found?

Old World Fruit bats

Pteropodidae

In the Old World Tropics.

How many families are in Microchiroptera?

17.

How do most Pteropodidae (in the suborder megachiroptera)(world fruit bats) navigate?

They primarily use vision to navigate (“orientate visually”) rather than echolocation.

Do Pteropodidae (in the suborder megachiroptera) use echolocation? What is the exception?

Most do not echolocate, unlike many other bats.

An exception is the genus Rousettus, which uses echolocation by clicking its tongue against the sides of its mouth.

How large can bats in the genus Pteropus (Pteropodidae in the suborder megachiroptera) get?

Can get up to around 1.5kg in weight

Wingspan can grow to about 1.7 meters.

What is Microchiroptera?

A traditional suborder of bats (Order Chiroptera) comprising most bat species.

What proportion of Microchiroptera are small-bodied?

About 70% weigh less than 20 g.

What is the typical weight threshold defining most Microchiroptera as small?

Less than 20 g.

What is the smallest mammal in the world within Microchiroptera? How much does it weigh?

The bumblebee bat.

About 2 g.

What type of echolocation do all Microchiroptera use? Describe it.

Laryngeal echolocation: which is echolocation produced using sound generated in the larynx.

What do Microchiroptera use echolocation for?

Orientation, and in many species, prey detection.

What does it mean that bats are monophyletic?

They all descend from a single common ancestor.

Which bats are genetically closer to Pteropodidae than to other microbats?

Horseshoe bats.

What are the two modern bat suborders based on genetic data?

Yinpterochiroptera and Yangochiroptera.

Which groups are included in Yinpterochiroptera?

Pteropodidae (fruit bats) + horseshoe bats and their relatives.

What does Yangochiroptera include?

The remaining bats previously classified as Microchiroptera.

How old are some of the earliest known bat fossils?

About 52.5 million years old.

What does Icaronycteris tell us about early bat evolution?

It had well-developed wings, indicating early evolution of flight.

What is significant about Onychonycteris finneyi compared to modern bats?

It had claws on all digits and shows more primitive features.

What is a bat wing a modification of?

The bat wing is a modified version of the pentadactyl limb (the standard five-digit limb found in most vertebrates).

What makes bats unique among mammals?

They are the only mammals capable of powered flight.

What does bat wing shape determine?

Wing-shape determines flight speed and manoeuvrability.

What type of wing shape do fast-flying bats have?

Long, narrow wings.

What is the effect of long, narrow wings on drag?

They reduce drag.

What is wing loading?

The amount of body weight carried per unit wing area.

Do fast-flying bats have high or low wing loading?

High wing loading.

What is a disadvantage of high wing loading? Why is this a disadvantage?

Low manoeuvrability.

Because their wing shape and high wing loading favour speed over turning ability.

Where do bats with low aspect ratio wings typically fly?

In forests or confined/cluttered environments.

What does a low aspect ratio wing look like?

Short and broad.

Do manoeuvrable forest bats have high or low wing loading?

Low wing loading.

What does low wing loading allow bats to do?

Fly slowly and turn easily.

What is a key advantage of low wing loading? What is the disadvantage of low wing loading?

Advantage: High manoeuvrability in small spaces.

Disadvantage: Slower and less efficient flight over long distances.

Why are high-frequency sounds useful in bat echolocation?

They have short wavelengths that detect small objects.

What structure helps bats capture insects during flight?

Most insect-eating bats catch prey while flying.

• The wing and tail membrane (uropatagium) helps form a kind of “net” to trap insects.

What adaptations have insects evolved as defences against bats?

In response, many insects have evolved defences against bats:

• They can hear ultrasound (bat echolocation calls).

• If a bat is far away, they may veer away from its direction.

• If a bat is close, they may perform erratic movements or spirals to escape.

What is gleaning in bats?

Catching prey from surfaces rather than in flight.

Why is echolocation less effective for gleaning?

Complex surfaces create confusing echoes.