1.
Homologous
trait shared between Whales and Chimpanzees
a.
Whale
is a generic name for a group of marine mammal, including dolphins, porpoises,
sperm whale, killer whale, pilot whale, and beluga whale, to name a few. Whales
are decedents of land-living mammals from the Aritodactyl order. Whales evolved
from Ambulectus going fully aquatic about 5-10 million years ago. Whales, like mammals,
are warm blooded; they nurse their young, have hair, and have lungs which breathe
air.
Chimpanzees
are members of the Hominidae family, along with humans. Chimps live on land and
walk upright on two legs when carrying things. They are covered in black hair
with a bare face, fingers, toes, and have palms on hands and feet. They have
strong family bonds and wean infants by about three years old, maintaining a
close relationship with their children. They reach puberty around 10 and
generally live to around 50 years old. Chimpanzees live in West and Central
Africa and are currently, sadly, on the endangered species list.
b.
Homologous
trait: One aquatic and one land living:
The
homologous trait between the two species is their forelimbs. Whales and
Chimpanzees, along with humans, birds, and reptiles, all share a common
four-legged ancestor, the tetrapod. Having lived over 365 million years ago the
tetrepod is a common ancestor that is responsible for the forelimbs found in
the listed groups, including whales and chimpanzees. Whales’ forelimbs are
structured as flippers. They are a flat broad limb adapted for swimming. Whale
flippers differ slightly between each sub-category of whales. For instance
killer whales have Pectoral flippers with a skeleton of forelimb land mammals. Their flippers are rounded and paddle like,
used for steering and stopping. They have a thick cartilage that pads the
bones. Humpback whales have flippers with bumpy edges, yet provide the whale the
ability to channel flow and increase aerodynamic efficiency. The structure of
the whales forelimbs are greatly different to that of the chimpanzees in that
the skeletal structure is padded by a cartilage and rough, rigid surface
forming a rounded shape. The function is different because whales use their
forelimbs to help them swim and maneuver through water. Chimpanzee’s forelimbs
are structured the same in that they have the same skeleton structure humerus,
ulna, radius, carpals and phalanges, but they are housed differently which accounts
for the different functions. Chimpanzees’
forelimb skeletal structure is housed in muscle, flesh and fur. The phalanges
are detached allowing for fingers on the palmed hand. The elbow joint moves
too, just as a human. These structural differences allow for the difference in
function. Chimpanzees use their forelimbs for climbing trees, carrying things
or babies, and for walking.
c.
Whales
and Chimpanzees are ancestors from a four-legged animal called the tetrapod,
which produced the forelimb homologous trait found in these species. A tetrapod
are vertevrate animals with four limbs, so I know that the tetrapod had that
trait.
Killer Whale
Humpback Whale
Chimpanzee
2.
Analogous
trait shared between Sugar Gliders and Flying Squirrels
a.
A
Sugar Glider is a small gliding possum and originates from the marsupial
family, like kangaroos. They live in the eastern and northern mainland of
Australia as well as New Guinea. They have a squirrel-like body with a long
tail. They have five digits on each foot, equipped with claws. They have large
eyes and the females have a marsupium, (pouch) for carrying their babies
because marsupial species give birth to babies who are not fully developed.
The
name, Flying Squirrel, can be misleading as they are not capable of actual
mechanical flight like birds, but they are capable of gliding. They live in
North America and are part of the placental family. They bare a strong physical
appearance to Sugar Gliders in that they have a tail and five-digit feet with
large eyes. They do not have a pouch however because mammals in the placental
family give birth to fully developed babies.
b.
Analogous
trait: Both gliders, yet not from the same family.
The
analogous trait shared by Sugar Gliders and Flying Squirrels is the thin piece
of skin that stretches from their feet to their hands, allowing the small fur
balls to glide from tree to tree. The trait of “wings” evolved in each species
independently as a product of their environment. Both species are tree dwellers
who adapted the paper-like wings to allow a gliding movement from on tree to
another. Flying squirrel produce more lift and less drag with their wings than
Sugar Gliders and they have a well-developed propatagium in the structure of
their forewing. Sugar Gliders have this as well but it is smaller. Regardless
of size and performance, both the Sugar Glider and the Flying Squirrel have
this trait which allows them to glide in their environment.
c.
Sugar
Gliders, from the marsupials family, and Flying Squirrels, from placental, are thought
to have come from a common ancestor over 100 million years ago and
independently evolved ever since. The
group was mammal which diverged into the two groups, placental and marsupials. According
to a website at UC Berkley “Since sugar gliders and flying squirrels are very
distantly related [100 mya], it seems very unlikely that their common ancestor
had flaps of skin stretched between its legs…. Instead, each lineage probably
evolved the trait independently as adaptations for gliding and tree-living” (evolution.berkley.edu).
The quote basically explains that because these mammals lived so far apart and
branched off from their common ancestor over 100 mya, than the probability of
having an ancestor possessing the “paper-wing” trait is highly unlikely. It is
more likely that the Sugar Glider and the Flying Squirrel, through parallel evolution,
evolved with “wings” to be more “fit” for their environment.
d.
Pictures
Sugar Glider
Flying Squirrel
