Exam 2 Chapter 27

Given the simplified metazoan phylogenetic tree below, which statement about the evolutionary relationship between the animals is not true? a)Bats are more closely related to wolves than bears. b)Elephants and bears share a common ancestor. c)Lions and bears share a more recent common ancestor than bats and wolves. d)Bear genomes are more similar to wolf genomes than elephant genomes.

a)Bats are more closely related to wolves than bears.

An animal embryo develops as a triploblast eucoelomate with spiral cleavage. The animal is most likely a(n) ______. a)Chordate b)Arthropod c)Ctenophore d)Nematode

b)Arthropod

Why is it difficult for scientists to assess the development of animals before the Cambrian Era? a)Most animals were too small to be seen in the fossil record. b)Most animals were soft-bodied, limiting the fossil record. c)The fossil record of earlier eras has been lost to erosion. d)The animals were all aquatic, so fossil records are lost to the bottom of the oceans.

b)Most animals were soft-bodied, limiting the fossil record.

What can be inferred from the observation that Hox genes are highly conserved among bilaterian animals? a)Hox genes have not experienced evolutionary pressure. b)The same genes are needed to control body plan development in most bilaterians. c)The last common ancestor of the bilaterians expressed Hox genes. d)Hox gene expression is the simplest way to control bilaterian body plans.

b)The same genes are needed to control body plan development in most bilaterians.

All vertebrates have bilateral symmetry and a true coelom. At the base of the phylogenetic tree, neither sponges nor cnidarians have a coelom. Sponges have an asymmetric body plan; cnidarians have radial symmetric plan. What advantages do the bilateral symmetry and the coelom give to animals? a)Bilateral symmetry allows animals to move sideways. The coelom is not a distinct advantage. b)Radial symmetry is actually more efficient because animals can move easily in several directions. The coelom cushions internal organs. c)Bilateral symmetry allows for directional motion. The coelom cushions organs and allows freedom of motion. d)Bilateral symmetry is associated with directional motion and hunting. The coelom is an inefficient structure because it is a waste of space.

c)Bilateral symmetry allows for directional motion. The coelom cushions organs and allows freedom of motion. Bilateral symmetry and the coelom contributed to the development of complex animals.

If Hox genes are mutated or duplicated, can that lead to the diversification of appearance in animals? a)Any change in the Hox genes will lead to the death of the organism. No new traits will appear in the population. b)Hox genes do not play a significant role besides encoding specific structural proteins. c)Mutations in Hox genes can lead to considerable changes in body anatomy and physiology and are considered an engine of evolution. d)Hox genes are activated late during development and do not affect appearance or basic body plan in an animal.

c)Mutations in Hox genes can lead to considerable changes in body anatomy and physiology and are considered an engine of evolution. Modifications in Hox genes produce large changes in the body plan of animals. They are considered one of the main factors in the diversification of animal morphology by modifying basic body plans.

Some people can mistakenly classify sharks and tuna in the same class. What is the main reason for such an error? a)Sharks and tuna are both fast swimming fish. b)Sharks and tuna have the same diet. c)Sharks and tuna have similar body plans as a result of convergent evolution because they are fast swimmers and predators. d)Sharks and tuna are salt water fish.

c)Sharks and tuna have similar body plans as a result of convergent evolution because they are fast swimmers and predators. Convergent evolution leads to similar adaptations which can be mistaken for relatedness.

A paleontologist claims that most extant animal phyla appeared during the Cambrian. Is the claim correct? a)No, all phyla went extinct during the mass extinction and new phyla arose. b)No, the phyla that survived the Paleozoic period were wiped out by the massive extinction that followed an asteroid impact at the end of the Mesozoic. c)Yes, massive extinction did not kill all species. The survivors in each phylum continued to evolve and occupy niches vacated by the species that disappeared. d)Yes, there is a constant level of extinction and new species arise to replace those that disappear.

c)Yes, massive extinction did not kill all species. The survivors in each phylum continued to evolve and occupy niches vacated by the species that disappeared. Some species in each phylum survived, continued to evolve and occupy new niches. Massive extinction events are often followed by species radiation.

A student is classifying humans according to symmetry, germ layers, coelom, cleavage, embryological development. After some thought, she comes up with these possible answers. Which one is correct? a)radial symmetry three germ layers pseudocoelomate radial cleavage of embryo cleavage protostome b)bilateral symmetry diploblastic eucoelomate spiral symmetry of embryo cleavage protostome c)bilateral symmetry triploblastic eucoelom radial symmetry of embryo cleavage deuterostome d)radial symmetry triploblastic acoelomate radial symmetry of embryo cleavage deuterostome

c)bilateral symmetry triploblastic eucoelom radial symmetry of embryo cleavage deuterostome This is the classification of humans.

Students prepare a proposal to support the fact that humans belong to the animal kingdom. Which arguments would uphold the hypothesis that humans are animals too? a)Humans display alternation of generation going from diploid adults to haploid spores, and from haploid spores to haploid gametes which fuse to form a zygote at fertilization. b)Humans, like other animals, do not have specialized tissues. c)Humans are autotrophs, and we synthesize our own food. d)Humans display all the characteristics of animals including multicellularity, specialized tissues, heterotrophy, sexual reproduction, and body plan modulated by Hox genes.

d)Humans display all the characteristics of animals including multicellularity, specialized tissues, heterotrophy, sexual reproduction, and body plan modulated by Hox genes. Humans have all the characteristics of animals.

Which of the following explanations is not correct regarding the Cambrian explosion? a)The level of oxygen in the atmosphere rose drastically during the Cambrian. b)Continental shelf exposed by glacier retreat created numerous shallow lagoons or pools that made possible biodiversity of animals. c)The prey-predator relationships exerted selective pressures leading to species radiation and colonization of new habitats. d)Massive glaciation changed the climate of the Earth.

d)Massive glaciation changed the climate of the Earth. Ice ages are associated with extinction, not diversification of species. Temperatures were mild during the Cambrian.

Mass extinction events are often followed by short bursts of rapid species diversification and expansion. How do mass extinctions promote rapid evolution? a)Resources that were available before the mass extinction are no longer found in the environment. b)Animals need to adjust to new climate patterns. c)Plant death forces new species to become producers. d)New niches are available to be colonized by surviving animals.

d)New niches are available to be colonized by surviving animals.