Biology 32 33 34
Terms in this set (47)
1. Summarize the main stages of animal development. What family of control genes plays a major role?
a. In most animals, the zygote undergoes cleavage, which leads to the formation of a blastula. Next, in gastrulation, one end of the embryo folds inward, producing layers of embryonic tissue, as the cells of these layers differentiate, a wide variety of animal forms result. Despite the diversity of animal forms, animal development is controlled by a similar set of Hox genes across a broad range of taxa.
2. Put the following milestones in animal evolution in chronological order from oldest to most recent: origin of mammals, earliest evidence of terrestrial arthropods, ediacaran fauna, extinction of large, nonflying dinosaurs
a. Ediacaran fauna
b. Earliest eveidence of terrestrial arthropods
c. Origin of mammals
d. Extinction of large, nonflying dinosaurs
3. Distinguish between the terms grade and clade.
a. Grade- group of animal species that share the same level of organizational complexity
b. Clades- derived characteristics that originated in a common ancestor and were passed on to the various descendents
4. Compare three aspects of the early development of a snail (a mollusk) and a human (a chordate).
a. A snail has a spiral and determinate cleavage pattern; a human has a radial, indeterminate cleavage
b. In a snail the coelomic cavity is formed by splitting the mesoderm masses; in humans the coelom forms from folds of archenteron.
c. In snails the mouth forms from blastospore; in human the anus develops from blastospore.
.5. Describe the evidence that cnidarians share a more recent common ancestor with other animals than with sponges.
a. Cnidarians possess true tissues while sponges do not. Also unlike sponges cnidarians exhibit body symmetry, though it is radial and not bilateral as in other animal phyla
6. How do the phylogenetic hypotheses differ in structuring the major branches within the clade Bilateria?
a. The morphology-based tree divides Bilateria into 2 major clades: deuterostomia and protostomia. The molecular-based tree recognizes three major clades: deuterostomia, Ecdysozoa, and Lophotrochozoa
7. Describe key ways that distinguish animals from plants and fungi.
a. Unlike animals, which are heterotrophs that ingest their food, plants are autotrophs, and fungi are heterotrophs that grow on their food and feed by absorption. Animals lack cell walls, which are found in both plants and fungi. Animals also have muscle tissue and nerve tissue, which are not found in either plants or fungi. In addition, the sperm and egg cells of animals are produced by meiotic division, unlike what occurs in plants and fungi (where reproductive cells such as sperm and eggs are produced by mitotic division). Finally, animals regulate the development of body form with Hox genes, a unique group of genes that is not found in either plants or fungi.
8. What caused the Cambrian explosion? Describe current hypothesis?
a. Current hypotheses about the cause of the Cambrian explosion include new predator-prey relationships, an increase in development flexibility provided by the origin of Hox genes and other genetic changes.
9. Describe how body plans provide useful information yet should be interpreted cautiously when scientists are trying to understand evolutionary relationships.
a. Body plans provide a helpful way to compare and contrast key features of organisms. However, phylogenetic analyses show that similar body plans have arisen independently in different groups of organisms. As such, similar body plans may have arisen by convergent evolution and hence may not be informative about evolutionary relationships.
10. Describe the data and methods used today to reconstruct animal phylogeny.
a. To reconstruct the evolutionary history of animal life, researchers collect morphological and molecular data and use cladistic methods to analyze that data. In a cladistic approach shared derived (morphological and molecular) characters are used to place organisms into a nested hierarchy of monophyletic clades.
1. Describe how sponges feed.
a. The flagella of choanocytes draw water through their collars, which trap food particles. The particles are engulfed by phagocytosis and digested, either by choanocytes or amoebocytes.
2. Compare and contrast the polyp and medusa forms of cnidarians.
a. Both the poly and medusa are composed of an outer epidermis and inner gastrodermis separated by a gelatinous layer, the mesoglea. The polyp is a cylindrical form that adheres to the the substrate by its aboral end; the medusa is a flattened, mouth-down form that moves freely in the water.
3. Describe the structure and function of the stinging cells for which cnidarians are named.
a. Cnidarian stinging cells (cnidocytes) function in defense and prey capture. They contain capsule like organelles (cnidae), which in turn contain coiled threads. The threads either inject poison or stick to and entangle small prey.
Explain how tapeworms can survive without a coelom, a mouth, a digestive, or an excretory.
a. Tapeworms can absorb food from their enciroment and release ammonia into their environment through their body surface because their body is very flaty, due in part to the lack of a coelom.
5. Annelid anatomy can be described as "a tube within a tube." Explain.
a. The inner tube is the alimentary canal, which runs the length of the body. The outer tube is they body wall. The two tubes are separated by the coelom.
7. Describe two adaptations that have enabled insects to thrive on land.
a. The arthropod exoskeleton, which had already evolved in the ocean, allow terrestrial species to retain water and support their own bodies on land. Wings allow them to disperse quickly to new habitats and to find food and mates. The tracheal system allows for efficient gas exchange despite the presence of an exoskeleton.
How do nematode and annelid body plans differ?
a. Nematodes lack body segments and a true coelom; annelids have both.
8. In contrast to mammalian jaws, which move up and down, the mouthparts of arthropods move side to side. Explain this feature of arthropods in terms of the origin of their mouthparts.
a. Arthropod mouthparts are modified appendages, which are bilaterally paired. As a result, the mouthparts come into contact by moving laterally, not up and down.
How do sea star tube feet attach to substrates?
a. Each tube foot consists of an ampulla and a podium. When the ampulla squeezes it forces water into the podium, which causes the podium to expand and contact the substrate.
Lacking tissues and organs, how do sponges accomplish tasks such as gas exchange, nutrient transport, and waste removal?
a. The sponge body consists of two layers of cells, both of which are in contact with a water. As a result, gas exchange and waste removal occur as substances diffuses into and out of the cells of the body, Choanocytes and amoebocytes ingest food particles from the surrounding water. Choanocytes also release food particles to amoebocytes which then digest the food particles and deliver the nutrients to the other cells.
Describe the cnidarian body plan and its two major variations.
a. The cnidarians body plan consists of a sac with a central digestive compartment, the gastrovascular cavity. The single opening to this compartment serves as both the mouth and the anus. The two main variations on this body plan are sessile polyps (which adhere to the substrate at the end of the body opposite to the mouth/anus) and motile medusa (which move freely through the water and remble flattened, mouth-down versions of polyps).
Is the lophotrochozoan clade united by unique morphological features shared by all of its members? Explain
a. No. Some lophotrochozoans have a crown of ciliated tentacles that function in feeding (called a lophophore), while others go through a distinctive developmental stage known as trochophore larvae. Many other lophotrochozoans do not have either of these features. As a result the clade is defined primarily by DNA similarities, not morphological similarities.
Describe ecological roles of nematodes and arthropods.
a. Many nematode species live in soil and in sediments on the bottom of bodies of water. These free-living species play important roles in decomposition and nutrient cycling. Other nematodes are parasites including many species that attack the roots of plants and some that attack animals (including humans). Arthropods have profound effects on all aspects of ecology. In aquatic environments, crustaceans play key roles as grazers (of algae), scavengers and predators and some species such as krill are important sources of food for natural world that are not affected in some way by insects and other arthropods such as spiders and ticks. There are more than 1 million species of insects, many composers and vectors of disease. Insects are also key sources of food for many organisms, including humans in some regions of the world.
You've read that echinoderms and chordates are closely related and have evolved independently for over 500 million years. Explain how both of these statements can be correct
a. Echinoderms and chordates are both members of deuterostomia, one of the three main clades of bilaterian animals. As such, chordates (including humans) are more closely related to echinoderms than we are to animals in any of the other phyla covered in this chapter nevertheless, echinoderms and chordates, but it does make clear that "close" is a relative term indicating that these two phyla are more closely related to each other than either is to animal phyla not in Deuterostomia.
Identify four derived characters that all chordates have at some point during their life.
a. Notochord, dorsal; hollow nerve cord; pharyngeal slits or clefts; muscular post anal tail
2. You are a chordate yet you lack most of the main derived characters of chordates. Explain.
a. In humans these character are present only in the embryo, the notochord becomes disks between the vertebrae, the tail is almost completely lost, and the pharyngeal clefts develop into various adult structures
What characteristics do hagfishes have that lancelets and tunicates lack?
a. Hagfishes have a head and skull made of cartilage, plus a small brain, sensory organs, and tooth-like structures. They have a neural crest, gill slits, and more extensive organ systems. In addition, hagfishes have slime glands that ward off predators and may repel competing scavengers.
How are differences in the anatomy of lampreys and conodonts reflected in each animal's feeding method?
a. Lampreys have round rasping mouth, which they use to attach to fish. Conodonts have two sets of mineralized dental elements, which may have been used to impale prey and cut it into smaller pieces.
What derived characters do sharks and tuna share? What are some characteristics that distinguish tuna from sharks?
a. Both are gnathostomes and have jaws, four clusters Hox genes, enlarged forebrains, and lateral line systems. Shark skeletons consist mainly of cartilage, whereas tuna have bony skeletons. Sharks also have a spiral valve. Tuna have an operculum and a swim blasser, as well as flecible rays supporting their fins.
6. Describe key adaptations of aquatic gnathostomes.
a. They have jaws;forelimbs modified to paired/unpaired fins and presence of tail for locomotion in water; streamlined body for cutting the water currents; swim bladders to maintain buoyancy in water
Describe the origin of tetrapods and identify some of their key derived traits.
a. Major tetrapod evolution occurred during the Devonian and the carboniferous periods, as modifications of the pre-existing forms, lineages of the lobe fins are considered to be the most close relatives of tetra pods, which developed limbs but still had adaptations for aquatic life. Therefore suggesting that the early tetra pods were aquatic organisms with limbs. The other derived traits include development of rest which separates rest of the body from the head, pelvic girdle and absence of gills slits.
8. Some amphibians never leave the water, whereas others can survive in relatively dry terrestrial environments. Contrast the adaptations that facilitate these two lifestyles.
a. Adaptations for aquatic life: gills for life in water; have lateral line system; they retain larval features for life in water as adults
b. Adaptations for terrestrial life: moist skin for Cutaneous respiration and lungs for aerial respiration; these protect their eggs with foam nests, viviparity and other adaptations; developed two pairs of legs for hopping; avoid dehydration by burrowing or living under moist leaves
Describe 3 key amniote adaptations for life on land.
a. Tough impermeable exoskeleton; shelled eggs containing four specialized membranes the amnion, chorion, the yolk sec, and allantois. These eggs rule out the important of external water and also protects the egg beside providing nourishments, gas exchange and removal of waste; development of rib-cage for ventilation of lungs
10. Are snakes tetra pods? Explain.
a. Yes. Although they do not have visable limbs in their adult stages of life, in the embryonic stage, snakes did have four limbs classifying them as tetra pods.
11. Identify four avian adaptations for flight.
a. Forelimbs are modified into wings which facilitate flight; absence of heavy jaws and teeth are the adaptations that trim the weight of the head for an efficient flight; the absence of urinary bladder and presence of only single ovary is also an adaptation to flight; bones are pneumatic, light and strong
Contrast monotremes, marsupials, and eutherians in terms of how they bear young.
a. Monotremes: these are primitive egg laying mammals which have mammary glands but lack nipples.
b. Marsupials: these are the mammals that give birth to young ones which attach to the nipple in the mother's pouch and complete their development
c. Eutherians: they are viviparous mammals which have a well developed placenta for nourishing the fetus and undergo a period of gestation so that it delivers the young one in advance stage of development
13. Identify at least five derived characteristics of primates.
a. Primates have hands and feet adapted for grasping and their digits and have flat nails instead of narrow claws as of other mammals
b. primates have a large brain and short jaws with a flat face
c. they have forward looking eyes which are close together on the front of the face
d. all primates have a thumb and toe that is relatively mobile and separate from other fingers but anthropoids (monkeys and apes) have fully opposable thumb
e. primates have relatively well developed parental care and complex social behavior
Identify some characters that distinguish hominins from other apes.
a. Hominins include primates that were formerly called apes
b. Include gibbons gorillas chimpanzees and humans
c. Diverged from old world monkeys
d. Non human hominins are found exclusively in tropical regions of the old world
e. Except gibbons living hominins are larger than monkeys
f. Have relatively long arms short legs and no tail
g. Bipedal locomotion and relatively larger brains
15. Provide an example in which different features of organisms in the hominin evolutionary lineage evolved at different rates.
a. The hominin evolutionary lineage witnessed evolution of features at different rates as well as modification of features during the evolutionary lineage. For example the earliest hominids like australopethicus anamensis had a bipedal locomotion but brain size remained smaller than the homo sapiens of today
Describe likely features of the chordate common ancestor and explain your reasoning.
a. Lancelets are the most basal group of living chordates, and as adults they have derived key characters of chordates. This suggests that the chordate common ancestor may have resembled a lancelet in having an anterior end with a mouth along with the; pharyngeal slits or clefts; and a muscular post-anal tail; notochord; dorsal hollow nerve cord
Compare the typical lifestyle of craniates with that of lancelets and tunicates.
a. Craniates have a head and a more extensive muscular system than lancelets or tunicates, this allows them to coordinate and perform more complex behaviors. Basal craniates are scavengers that locate and feed on worms and dead or sick fishes. In contrast lancelets and tunicates feed by filtering the water for food particles
Identify the shared features of early fossil vertebrates.
a. Conodonts, among the earliest vertebrates in the fossil record, while jawless their well developed teeth provide early signs of bone formation. Other species of jawless vertebrates developed armor on the outside of their bodies probably to protect themselves from predators. Paired appendages for locomotion and an inner ear with semicircular canals which provided a sense of balance.
How would the appearance of organisms with jaws have altered ecological interactions? Provide supporting evidence.
a. The origin of jaws altered how fossil gnathostomes obtained food which in turn had great ecological impact. Predators could use their jaws to grab prey or remove chunks of flesh, stimulating the evolution of increasingly sophisticated means of defense in prey species. Evidence for these changes can be found in the fossil record which includes fossils of 10 meter long predators with remarkably powerful jaws.
Which features of amphibians restrict most species to living in aquatic or moist terrestrial habitats?
a. Amphibians require water for reproduction their bodies can lose water rapidly through their moist highly permeable skin; amphibian eggs do not have a shell and hence are vulnerable to desiccation
Explain why birds are considered reptiles.
a. Birds are descended from theropod dinosaurs and dinosaurs are nested within the archosaur lineage one of the two main reptiles. Thus, the other living archosaur reptiles, the crocodilians are more closely related to birds than they are to non- archosaur reptiles such as lizards.
Describe the origin and early evolution of mammals.
a. Mammals are members of a group of amniotes called synapsids. Early synapsids laid eggs and had a sprawling gait. The jaw was modified over time in non-mammalian synapsids, eventually coming to resemble that of a mammal. There were many species of early mammals but most of them awere small and they were not abundant or dominant members of their community. Mammals did not rise to ecolofical dominance until after the extinction of the dinosaurs.
Explain why it is misleading to portray human evolution as a "ladder" leading to Homo sapiens.
a. The fossil record shows that from 4.5 to 2.5 mya a wide range of hominin species walked upright but had relatively small brain sizes. About 2.5 mya the Homo genus emerged. These species used tools and had larger brains than those of earlier hominins fossil evidence indicates that multiple members of our genus were alive at any given point in time. Furthermore until about 1.3 mya these various homo species also coexisted with members of earlier hominin lineages such as paranthropus. The different hominins alive at the same periods of time varied in body size, body shape, brain size, dental morphology, and the capacity for tool use. Thus, human evolution is viewed not as a evolutionary path leading to homo sapiens but rather as an evolutionary tree with many branches.