Lesson 8: Evolution

Question 1

The theory of evolution was

first conceived by the British naturalist

Answer 1

Charles Darwin. Darwin’s theory explains how new
species come into existence, how organisms
become adapted to their environments, and
why specific groups of organisms share specific
traits.

Question 2

Heritable means

Answer 2

s that
the trait is part of an organism’s genetic code
and, therefore, either will be, or (depending on
the type of reproduction) has a chance to be,
copied to the organism’s offspring

Question 3

One source for new
heritable traits is random genetic mutation. In
order for selection to occur on any given trait,
there must be

Answer 3

variation in that trait in a

population

Question 4

natural environments have limited
resources, and __ for these resources
permits only some organisms to successfully
reproduce before they die.

Answer 4

competition

Question 5

The theory of evolution combines these four

basic principles of life together:

Answer 5

the differential
success of certain variations of a heritable trait,
because of competition for limited resources,
leads to the change over time (evolution) of
that trait in a population.

Question 6

While new
traits may be introduced by random mutations,
the determination of which traits are
successfully passed on to later generations is
not random. Instead, it is based on a specific
criterion:

Answer 6

how well each trait improves an

organism’s reproductive success.

Question 7

The competitive selective process by
which detrimental traits are competitively
discarded and advantageous traits are retained
is called

Answer 7

natural selection

Question 8

Organisms are grouped together based on their

most recent

Answer 8

shared common ancestors

Question 9

hadrosaurs, pachycephalosaurs, ceratopsians, ankylosaurs,

and stegosaurs are grouped together, and we call this group the

Answer 9

Ornithischia.

Question 10

These
ornithischians and the saurischians share a
more recent ancestor with each other than they
do with all other amniotes, and we call this
group

Answer 10

Dinosauria.

Question 11

all dinosaurs
are classified together in a group because all
dinosaurs evolved from a single species of

Answer 11

amniote tetrapod

Question 12

A character is

Answer 12

any heritable

trait that can be described and labeled

Question 13

shared derived character is

Answer 13

a character that is
present in two or more groups and their
common ancestor, but is not present in any
more distantly related groups

Question 14

A shared derived

character is also called a

Answer 14

synapomorphy.

Question 15

f ornithischians have a
special bone in the lower jaw that forms a beak,
called the

Answer 15

predentary, and no other dinosaurs
have this special beak bone. Thus, the character
of the predentary was passed on to all
ornithischians from their ancient shared
ancestor and is a synapomorphy

Question 16

Ouranosaurus is an

Answer 16

iguanodont with a beak and
grinding teeth, hoofed toes, and long processes
on the vertebrae of the back that form a sail.

Question 17

Spinosaurus has the __ hip

Answer 17

saurischian hip

arrangement where the pubis points forwards

Question 18

Ouranosaurus has the __hip

Answer 18

ornithischian hip
arrangement where the pubis points
backwards.

Question 19

Spinosaurus and Ouranosaurus both
have a sail, but we do not consider the sail to be
__, or __,
between Spinosaurus and Ouranosaurus.

Answer 19

synapomorphy, or shared derived character

Question 20

Spinosaurus has many of the synapomorphies

of __ and __.

Answer 20

saurischians and theropods

Question 21

Ouranosaurus has many of the synapomorphies

of __ and __.

Answer 21

ornithischians and ornithopods

Question 22

Therefore,
the most likely evolutionary scenario is that the
sail in Spinosaurus evolved __of the
sail in Ouranosaurus

Answer 22

independently

Question 23

The evolution of similar traits in

two different lineages is termed

Answer 23

convergent

evolution.

Question 24

The idea that “all
other things being equal, the simplest answer is
usually the right one” is called

Answer 24

parsimony. Parsimony is also referred to as Occam’s razor. It is simpler to assume that the one character in common between Ouranosaurus and Spinosaurus (the sail) is the result of convergent evolution, than it would be to
assume that the huge number of similarities
between Ouranosaurus and iguanodonts are all
the result of convergence.

Question 25

. The
resulting arrangements look like diagrams of a
“family tree” and are called

Answer 25

phylogenetic trees

Question 26

Phylogenetic trees are composed of

Answer 26

nodes and

branches

Question 27

A group of species that share a

common node is called a

Answer 27

clade. Clades can be
very small (even as small as two species), or
very large – there are no size limits. A clade
must contain the ancestor of a group and all of
its descendants. A group that does not include
all of the descendants of a common ancestor is
therefore not a clade.

Question 28

Thomas Henry Huxley was a close colleague of

Charles Darwin and one of the earliest

Answer 28

advocates for the theory of evolution. Huxley
was also the first scientist to recognize that
birds evolved from dinosaurs, and he cited the
newly discovered specimens of Archaeopteryx
as fossils of a “missing link” between dinosaurs
and birds.

Question 29

Archaeopteryx has long wing-feathers and tail
feathers just like a bird, but they also show that
Archaeopteryx had

Answer 29

teeth, clawed fingers, and a

long series of tail vertebrae just like a dinosaur

Question 30

Sinosauropteryx was the first

Answer 30

non-avian (non-bird) dinosaur to be discovered

with feathers.