gUidE:

Nov. 29 - Concept check 28.1

Dec. 1 - Concept check 28.2 - 28.8 & Concept check 27.1 - 27.5

Dec. 8 - Concept check 29.1 - 29.4 & Concept check 30.1 - 30.4

Dec. 9 - Concept check 31.1 - 31.5

Dec. 10 - Concept check 24.1 - 24.3 & Concept check 26.1 - 26.6

Concept 26.6

Q1: Which kingdoms in Whittaker’s five- kingdom system include organisms now in the domain Eukarya?

A1: Protista, Plantae, Fungi, Animalia

Q2: Based on Figure 26.22, explain why the kingdom Monera is no longer considered a valid taxon?

A2: Monera included both bacteria and archaea, but archaea are more closely related to eukaryotes than to bacteria.

Concept 26.5

Q1: How does the division of function differ for single-celled and multicellular organisms?

A1: A single-celled organism must carry out all of the functions required to stay alive. Most multicellular organisms have many types of specialized cells, and life functions are divided among specific cell types.

Q2: In what way is “Cambrian explosion” a good description of the early part of the fossil record of animal history? What is meant by the metaphor of a “long fuse” for the Cambrian explosion?

A2: Fossils of most major animal phyla appear suddenly in the first 20 million years of the Cambrian period. Molecular clocks suggest that many animal phyla originated much earlier.

Concept 26.4

Q1: What evidence supports the hypothesis that mitochondria preceded plastids in the evolution of eukaryotic cells?

A1: All eukaryotes have mitochondria or genetic remnants of these organelles, but not all eukaryotes have plastids.

Q2: How is a eukaryotic cell like a chimera?

A2: The chimera of Greek mythology contained parts from different animals. Similarly, a eukaryotic cell contains parts form various prokaryotes; mitochondria from one type, and bacterium, plastids from another type, and a nuclear genome from parts of the genomes of these endosymbionts and at least one other cell.

Concept 26.3

Q1: What do fossilized stromatolites suggest about the evolution of prokaryotes?

A1: Prokaryotes must have existed at least 3.5 b.y.a, when the oldest fossilized stromatolites were formed.

Q2: The first appearance of free oxygen in the atmosphere must have triggered a massive wave of extinctions among the prokaryotes of the time. Why?

A2: Free oxygen attacks chemical bonds and can inhibit enzymes and damage cells. Some organisms were able to survive in anaerobic habitats, however.

Concept 26.2

Q1: Your measurements indicate that a fossilized skull you unearthed has a carbon-14/ carbon-12 ratio about ¼ that of the skulls of present-day animals. What is the approximate age of the fossilized skull?

A1: 22,920 years (four half-life reductions)

Q2: Based on Table 26.1, how long did prokaryotes inhabit Earth before eukaryotes evolved?

A2: About 1,300 million years, or 1.3 billion years.

Concept 26.1

Q1: What hypothesis did Miller and Urey test in their experiment?

A1: The hypothesis that conditions on the early Earth could have permitted the synthesis of organic molecules from inorganic ingredients.

Q2: Why was the appearance of protobionts surrounded by membranes likely a key step in the origin of life?

A2: In contrast to random mingling of molecules in an open solution, segregation of molecular systems by membranes could concentrate organic molecules, and electrical charge gradients across the membrane could assist biochemical reactions.

Q3: What is ribozyme?

A3: A ribozyme is an RNA molecule that catalyzes a chemical reaction

Concept 24.3

Q1: How can the Darwinian concept of descent with modification explain the evolution of such complex structures as the vertebrate eye or heart?

A1: Such complex structures do not evolve all at once, but in increments, with natural selection selecting for adaptive variants of the earlier versions.

Q2: Explain why the concept of exaptation does not mean that a structure evolves in anticipation of some future environmental change.

A2: Although an exaption is co-opted for new or additional functions in a new environment, it existed in the first place because it worked as an adaptation to the original environment.

Q3: How can heterochrony cause the evolution of different body forms?

A3: The timing of different development pathways in organisms can change in different ways (heterochrony). This can result in differential growth patterns, such as those producing different patterns of webbing in salamander feet.

Concept 24.2

Q1: Explain why allopatric speciation would be less likely to occur on an island close to a mainland than on a more isolated island of the same size.

A1: Continued gene flow between mainland populations and those on a nearby island reduces the chance that enough genetic divergence will take place for allopatric speciation to occur.

Q2: Normal watermelon plants are diploid (2n=22) but breeders have produce tetraploid (4n=44) watermelons. If tetraploid plants are hybridized with their diploid relatives, they produce triploid (3n=33) seeds. These offspring can produce triploid seedless watermelons and can be further propagated by cuttings. Are the diploid and tetraploid watermelon plants different species? Explain.

A2: The diploid and tetraploid watermelons are separate species. Their hybrids are triploid and as a result are sterile because of problems carrying out meiosis.

Q3: In the fossil record, transitional fossils linking newer species to older ones are relatively rare. Suggest an explanation for his observation.

A3: According to the model of punctuated equilibrium, in most cases the time during which speciation occurs is relatively short compared with the overall duration of the species' existence. Thus, on the vast geologic time scale of the fossil record, the transition of one species to another seems abrupt, and instances of gradual change in the fossil record are rare. Furthermore, some of the changes that transitional species underwent may not be apparent in fossils.

Concept 24.1

Q1: Two bird species in a forest are not known to interbreed. One species feeds and mates in the treetops and the other on the ground. But in captivity, the two species can interbreed and produce viable, fertile offspring. What type of reproductive barrier most likely keeps these species separate? Explain.

A1: Since the birds are known to breed successfully in captivity, the reproductive barrier in nature must be prezygotic. Given the species differences in habitat preference, the reproductive barrier is most likely to be habitat isolation.

Q2: a. Which species concept can be used for both asexual and sexual species?
b. Which can only be applied to sexual species?
c. Which would be most useful for identifying species in the field?

A2: a. All species concepts except the biological species concept can be applied to both asexual and sexual species because they define species on the basis of characteristics other than abitlity to reproduce.
b. The biological species concept can be applied only to extant sexual species.
c. The easiest species concept to apply in the field would be the morphological species concept because it is based only on the appearance of the organism. Additional information about its ecological habits, evolutionary history, and reproduction are not required.

Concept 31.5

Q1: What are some of the benefits that algae in lichens can derive from their relationship with fungi?

A1: A suitable environment for growth, retention of water and minerals, protection from sunlight, and protection form being eaten.

Q2: What characteristics of pathogenic fungi result in their being efficiently transmitted?

A2: A hardy spore stage enables dispersal to host organisms through a variety of mechanisms; their ability to grow rapidly in a favorable new environment enables them to capitalize on the host's resources.

Concept 31.4

Q1: What feature of chytrids supports the hypothesis that they represent the most primitive fungal lineage?

A1: Flagellated spores.

Q2: Why are glomeromycetes so ecologically significant?
Q3: Give different examples of how form fits function in zygomycetes, ascomycetes, and basidiomycetes.

A2: Most plants form arbuscular mycorrhizae with glomeromycetes; without the fungi, the plants would be poorly nourished.

Q3: Give different examples of how form fits function in zygomycetes, ascomycetes, and basidiomycetes.

A3: Zygomycetes - sturdy, thick-walled zygosporangium can withstand harsh conditions and then undergo karyogamy and meiosis when the environment is favorable for reproduction. Ascomycetes - the asexual spores (conidia) are produced in chains or clusters at the tips of conidiophores, where they are easily dispersed by wind. Basidiomycetes - basidiocarp supports and protects a large surface area of basidia, from which spores are dispersed.

Concept 31.3

Q1: Why are fungi classified as opisthokonts when most fungi lack flagella?

A1: The fungal lineage thought to be the most primitive, the chytrids, have posterior flagella, as do most other ophisthokonts. This suggests that other fungal lineages lost their flagella after diverging from the chytrid lineage.

Q2: Explain the evolutionary significance of the presence of mycorrhizae in the earliest vascular plants.

A2: This indicates that fungi had already established symbiotic relationships with plants by the time the first vascular plants evolved.

Concept 31.2

Q1: In terms of haploidy versus diploidy, how do the life cycles of humans and fungi differ?

A1: Majority of human life cycles are dominated by dipoid stages while in fungi, majority consists of haploid stages.

Q2: Suppose that you sample the DNA of two mushrooms on opposite sides of your yard and find that they are identical. What are two hypotheses that could reasonably account for this result?

A2: The 2 mushrooms might be reporoductive structures of the same mycelium. Or they might be parts of 2 separate organisms that have arised from a single organism through asexual reproduction and thus carry the same genetic information.

Concept 31.1

Q1: Compare and contrast the nutritional mode of a fungus with your own nutritional mode.

A1: Humans and fungus are heterotrophs. In humans, we ingest relatively large pieces of food and digest the food within our bodies. While in fungus, it digests its food externally and then absorbing the small molecules that result form digestion.

Q2: Describe how the structure of a fungus is adapted to its nutritional mode.

A2: The extensive network of hyphae puts a large surface area in contact with the food source, and rapid growth of the mycelium extends hyphae into new territory.

Concept 30.4

Q1: Explain why it is accurate to consider plant diversity to be a nonrenewable resource.

A1: Because extinction is irreversible, it decreases the total diversity of plants, many of which may have brought important benefits to humans. Such as in the field of medicine and agriculture.

Concept 30.3

Q1: It has been said that an oak tree is an acorn’s way of making more acorns. Write an explanation that includes these terms:
sporophyte
gametophyte
ovule
seed
ovaryfruit

A1: In the oak's life cycel, the tree (the sporophyte) produces flowers, which contain gametophytes in pollen grains and ovules; the eggs in ovules are fertilized; the mature ovaries develop into dry fruits called acorns; and the acorn seeds germinate, resulting in embryos giving rise to seedlings and finally to mature trees, which produce flowers then acorns.

Q2: Compare and contrast a pine cone and a flower in terms of structure and function.

A2: Pine cones and flowers both have sporophylls , modified leaves that produce spores. Pine trees have separate pollen cones (with pollen grains) and ovulate cones (with ovules inside cone scales). In flowers, pollen grains are produced by the anthers of stamens, and ovules are within the ovaries of carpels. Unlike pine cones, many flowers produce both the pollen and the ovules.

Q3: Explain the use of the terms monocot, dicot and eudicot.

A3: Recent molecular evidence pointed out that while monocots are a clade, dicots are not. Based on phylogenetic relationships, most dicots form a clade, now known as eudicots.

Concept 30.2

Q1: Based on Figure 30.4, explain why the various types of gymnosperms can be described as being similar yet distinctive.

A1: Although gymnosperms are similar in having "naked" seeds, their seed bearing structure vary greatly. For instance, Cycads have larger cones compared to Ginkgo and Gnetum. Leaf shape also varies greatly, from the needles of many conifers to the palmlike leaves of cycads to Gnetum leaves that look like those of flowering plants.

Q2: Explain how the pine life cycle (see Figure 30.6) reflects basic characteristics of seed plant.

A2: The life cycle illustrates heterospory, as ovulate cones produce megaspores and pollen cones produce microspores. The reduced gametophytes are evident in the formof the microscopic pollen grains and the microscopic female gametophyte within the megaspore. The egg is shown developing within an ovule, and the pollen tube is shown conveying the sperm. The figure also shows the protective and nutritive features of a seed.

Concept 30.1

Q1: Contrast sperm delivery in seedless vascular plants with sperm deliver in seed plants.

A1: To have any chance of reaching the eggs, the flagellated sperm of seedless vascular plants must rely on swimming through a film of water, usually limited to a range of less than a few centimeters. In contrast, the sperm of seed plants are produced within durable pollen grains that can be carried long distances by wind or by animal pollinators. Although flagellated in some species, the sperm of most seed plants do not require water because pollen tubes convey them directly to the eggs.

Q2: What additional features of seed plants, not present in seedless plants, contributed to the enormous success of seed plants on land?

A2: The reduced gametophytes of seed plants are nurtured by sporophytes and protected from stress, such as drought conditions and UV radiation. Pollen grains have tough protective coats and can be carried long distances, facilitating widespread sperm transfer without reliance on water. Seeds are more resilient than spores, enabling better resistance to environmental stresses and wider distribution.

Concept 29.4

Question:
I. What are a few key differences between seedless vascular plants and bryophytes?

Answers:
a) Bryophytes: have dominant gametophytes; are non-vascular plants. Seedless vascular plants: have dominant sporophyte; are vascular plants, and the evolution of true plants.

Question:
II. What is the major difference between most lycophytes and most ferns and their relatives?

Answer:
a) Most lycophytes have microphylls, whereas ferns and most fern relatives have megaphylls.