320 ■ CHAPTER 17 Animals and Human Evolution
REVIEWING THE SCIENCE
THE QUESTIONS
The Basics
(^1) Which of the following statements is not true?
(a) A single evolutionary line led from Ardipithecus ramidus to
modern humans.
(b) Some hominid traits evolved more rapidly than others.
(c) Brain size increased greatly from early hominids to Homo
sapiens.
(d) Toolmaking technology has improved greatly over the past
300,000 years.
(^2) The out-of-Africa hypothesis states that
(a) all new species of hominins arose in Africa and then migrated
to the rest of the world.
(b) many new species of hominins arose outside of Africa and then
migrated back to Africa later.
(c) all hominin speciation events occurred outside of Africa.
(d) all speciation events occurred in Africa, but only Homo sapiens
distributed itself across the globe.
(^3) Which of the following features do sponges lack that some
other animals have?
(a) segmented body plan
(b) symmetrical body plan
(c) backbone
(d) all of the above
(^4) Select the correct terms:
(Mitochondrial DNA / Nuclear DNA) is passed on only from the
maternal line. (Mitochondrial DNA / Nuclear DNA) is inherited from
both the mother and the father.
(^5) For each of the following cases, identify whether the animal
group has bilateral symmetry (B), radial symmetry (R), or no distinct
symmetry (N).
a. sponges
b. cnidarians
c. arthropods
d. chordates
e. primates
● (^) Animals are multicellular
ingestive heterotrophs. The
chordates include all animals
with a dorsal nerve cord.
Chordates with a backbone
are vertebrates, and all
other phyla of animals are
informally designated as
invertebrates.
● (^) Sponges lack distinct
symmetry; some
invertebrates have radial
symmetry; all other animals,
including all chordates, have
bilateral symmetry.
● (^) Many animal groups have
a body plan consisting of
repeated units known as
segments. Appendages,
body parts with specialized
functions, develop in pairs
from particular segments of
the body. The evolution of
segmentation and appendages
has allowed animals to exploit
new habitat and food sources
in novel ways.
● (^) Mammals are grouped
into three categories:
Eutherians are placental
and born in a well-developed
state. Marsupials have a
simple placenta and finish
development in a pouch.
Monotremes lack a placenta
and lay eggs.
● (^) Humans are mammals
(class), and more specifically
primates (order), having
flexible shoulder and elbow
joints, five functional fingers
and toes, opposable thumbs,
flat nails (instead of claws),
and large brains.
● (^) Hominins are characterized
by bipedalism, the ability to
walk upright on two legs.
They are a branch of the
apes, the hominids (family).
● (^) Mitochondrial-DNA
inheritance occurs
exclusively through the
maternal egg; the sperm
contributes essentially no
mitochondria and none of
the mitochondrial DNA.
Nuclear-DNA inheritance
occurs equally through
both the eggs and sperm;
all individuals have half
maternal and half paternal
nuclear DNA.