[ Pobierz całość w formacie PDF ]
Check Your Progress
1. List the three body parts of a mollusc.
2. List the main features of annelids.
3. List the five major features that have helped to make arthropods successful.
Answers:1. The mollusc s body has a visceral mass, a foot, and a mantle."
2. Annelids are segmented, with a complete digestive tract body plan. They contain a digestive system, clo-sed circulatory system, nervous system, and excretory
system." 3. Rigid, jointed exoskeleton; segmented body; well-developed nervous system; variety of respiratory organs; many go through metamorphosis.
1. Distinguish between the three types of mammals.
2.
List the two main features of mammals.
Answers:" 1. Monotremes lay eggs, marsupials have a pouch where newborn offspring finish development, and the offspring of placental mammals develop internally in
the uterus." 2. Mammary glands and hair are the two main features of mammals.
Check Your Progress
1. Describe how reptiles are adapted to reproduce on land.
2.
List the anatomical features of birds that help them fly.
3.
List the two main features of mammals.
Answers:1. Fertilization is internal in reptiles and results in the production of a leathery amniote egg.2. Birds forelimb
s are modified as wings; their bones are usually
hollow with air cavities; air sacs involved in respiration also lighten the body; and they have a well-developed nervous system and muscles."
3. Mammary glands and hair are the two main features of mammals.
Check Your Progress
1. What groups of animals are primates?
2. Did humans evolve from apes?
Answers:" 1. Prosimians, monkeys, apes, and humans are primates."
2. No, humans and apes share a common ancestor.
Figure 19.36" Evolutionary tree of primates.
MYA
The ancestor to all primates climbed into one of the first fruit-bearing forests about 66 . The descendants of this ancestor adapted to the new way of life and
developed such traits as a shortened snout and nails instead of claws. The time when the humans diverged from the ape line of descent is largely known from the fossil
MYA
record. A common ancestor was living at each point of divergence; for example, there was a common ancestor for monkeys, apes, and humans about 33 ; one for
MYA MYA
all apes and humans about 15 ; and one for just African apes and humans about 7 .
Figure 19.37" Human evolution.
The length of time each species existed is indicated by the vertical lines. Notice that there have been times when two or more hominids existed at the same time, such
as the three types of australopithecines shown. Therefore, human evolution resembles a bush rather than a single branch of a phylogenetic tree.
Check Your Progress
Contrast the australopithecines with Homo habilis.
Answer:" Australopithecines were apelike above the waist and humanlike below the waist. Homo habilis had a larger brain and smaller cheek teeth than the
australopithecines, and was able to use stone tools and possibly speech.
Figure 19.39" Evolution of modern humans.
a. The multiregional continuity hypothesis proposes that Homo sapiens evolved separately in at least three different places: Asia, Africa, and Europe. Therefore,
continuity of genotypes and phenotypes is expected in each region, but not between regions. b. The out-of-Africa hypothesis proposes that Homo sapiens evolved only
in Africa; then this species migrated and supplanted populations of Homo in Asia and Europe about 100,000 years ago.
Figure 19.38" Australopithecus afarensis.
a. A reconstruction of Lucy on display at the St. Louis Zoo.
MYA
b. These fossilized footprints occur in ash from a volcanic eruption some 3.7 . The larger footprints are double, and a third, smaller individual was walking to the side.
(A female holding the hand of a youngster may have been walking in the footprints of a male.) The footprints suggest that A. afarensis walked bipedally.
Check Your Progress
1. What are some distinctive features of Homo erectus compared to Homo habilis?
2. What is the out-of-Africa hypothesis?
3. Who were the Neandertals?
Answers:" 1. Homo erectus had a larger brain and flatter face, most likely a striding gait as we do, used fire, and made better tools." 2. The out-of-Africa hypothesis
proposes that Homo sapiens evolved only in Africa and then migrated to other parts of the world." 3. The Neandertals were a stocky and powerfully muscular people
capable of surviving harsh Ice Age conditions. They are believed to have been culturally advanced.
Figure 19.40" Cro-Magnons.
[ Pobierz całość w formacie PDF ]