Biology II CH 25 active reading guide

The Miller-Urey-type experiments demonstrate one way organic compounds may have been generated. What are some other hypotheses that show alternative situations?

-deep sea hydrothermal vents: areas on the sea floor where heated water & minerals gush from earths interior to the ocean -Alkaline vents: had a higher pH level (9-11) and warm water (40-90 degrees Celsius) rather than hot, a environment that may have been better suited for the origin of life -meteorites could have carried organic molecules. meteorite that hit Australia carried 80 amino acids

What were some challenges both plants and animals had to overcome in order to colonize land?

-reproduction on land -dehydration

Carbon-14 was used to establish the age of an ancient skeleton. The results showed that only 1/8 of the original carbon-14 isotope remained. Approximately how old is the skeleton? (Figure 25.6 in your text may help.)

1 half life of carbon 14 = 5,730 x the number of half lives (3) 5,730 x 3= 17,190

Use Figure 25.14 in your text to determine how many millions of years ago lineages A and B had the greatest diversity? (Hint: Draw a line straight up on the graph to find the point at which there are the most branches.)

1 million years

The current theory of the origin of life suggests that chemical and physical processes could have produced simple cells through a sequence of four main stages. Summarize them here.

1. the abiotic (nonliving) synthesis of small organic molecules, such as amino acids & nucleic bases 2. the joining of these small molecules into macromoleucles, such as proteins & nucleic acid 3. the packaging of these molecules into protocells, droplets with membranes that maintained an internal chemistry different from that of their surroundings 4. the origin of self-replicating molecules that eventually made inheritance possible

Summarize three lines of evidence that support the model of endosymbiosis.

1.The inner membranes of both organelles have enzymes and transport systems that are homologous to those found in the plasma membranes of living bacteria. 2. Mitochondria and plastids replicate by a splitting process that is similar to that of certain bacteria. In addition, each of these organelles contains circular DNA molecules that, like the chromosomes of bacteria, are not associated with histones or large amounts of other proteins. 3.As might be expected of organelles descended from free-living organisms, mitochondria and plastids also have the cellular machinery (including ribosomes) needed to transcribe and translate their DNA into proteins.

what is a reducing atmosphere?

A atmosphere with little oxygen

What are adaptive radiations?

Period of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles or niches in the communities. Ex: mammals were small, but once dinosaurs died out they grew in size and diversity, filling the role of the dinos.

What was most likely the first genetic material, DNA or RNA? __________

RNA

Explain the evidence for an early "RNA world."

RNA molecuels whole sequence best suites the surrounding environment & has the greatest ability to replicate itself will leave the most descendant molecules. natural selection would determine the most successful protocells.

What are ribozymes?

RNA molecules that function as enzymes

To date fossils outside the range of carbon-14 dating, researchers use other methods of establishing absolute fossil age. Explain how this can be done using radioisotopes with longer half-lives.

Radioisotopes become trapped in the layers if volcanic rock as it cools if the radioisotope has a longer half life than it deteriorates slower. if volcanic rock layers are determined to be between 525- 535 million years old than the fossil is about 530million years old

Could an eye be functional for a species if it could only determine light from dark?

Such eyes have no equipment for focusing images, but they do enable the animal to distinguish light from dark. Limpets cling more tightly to their rock when a shadow falls on them, a behavioral adaptation that reduces the risk of being eaten. "simple" eyes are quite adequate to support their survival and reproduction.

A mass extinction is the loss of large numbers of species in a short period, caused by global environmental changes. There have been five mass extinctions over the past 500 million years. What caused the Permian mass extinction 250 million years ago (mya)?

The Permian mass extinction occurred during the most extreme episode of volcanism in the past 500 million years. Geologic data indicate that (roughly half the size of Western Europe) in Siberia was covered with lava hundreds of meters thick.produced enough carbon dioxide to warm the global climate by an estimated , harming many temperature-sensitive species. The rise in atmospheric levels would also have led to ocean acidification,

How does species selection explain that not all evolutionary trends are linear?

The genus did not evolve in a straight line; it is the only surviving twig of an evolutionary tree that is so branched that it is more like a bush. The genus actually descended through a series of speciation episodes that included several adaptive radiations.

Explain evidence that changes in gene regulation may result in evolutionary changes rather than changes in a gene's sequence. Why is this significant?

a change in the regulation of a developmental gene may have fewer harmful side effects than a change to the sequence of the gene.

In 1953 at the University of Chicago, Stanley Miller and Harold Urey tested the Oparin-Haldane hypothesis with the apparatus you saw in Chapter 4, Figure 4.2. What was collected in the sample for chemical analysis? What was concluded from the results of this experiment?

a variety of amino acids and other organic compounds. results concluded that organic molecules could have formed on early earth as long as it was a reducing atmosphere. this lead to the hypothesis of the first organic molecules formed by volcanos.

The fossils of a whale in the Sahara Desert shown in Figure 25.1 in your text are an incredible find. The fossil record shows a pattern of how life changes on Earth much like the phylogenetic tree in the figure. Use the figure to answer the following: a. How many lineages from the phylogenetic tree end in extinction? b. What is the relationship between where a fossil is found in rock strata and its position on the phylogenetic tree? c. What are three large-scale processes that cause changes in the organisms on Earth over time? d. What happens during an adaptive radiation?

a. 10 b. c. continental drift, mass extinction, adaptive radiation d. a lineage gives rise to many new species

How old is the planet? _______________ How old is the earliest evidence of life on Earth? _______________. (Reminder: Place these events on your timeline.)

a. 4.6 billion years b. 3.5 billion years

Note the timeline represented as a circle in Figure 25.8 on pp. 532-533. a. Using the 1-hour timer analogy, when did prokaryotes originate? ______________ b. How many years ago did prokaryotes originate on the geologic timescale? _____________ c. When did the colonization of land occur on the timer scale? _______________ d. How many years ago was the colonization of land on the geologic timescale? _____________

a. about 45 minutes b.about 3.5 billion years c. about 7 minutes d. 0.5 billion years

Based on the movement of the continents over time, answer the following: a. What is the San Andreas Fault? b. Where was India 65 million years ago? c. What caused the uplift of the Himalayas? d. How can a fossil freshwater reptile be found in both Brazil and West Africa, areas separated today by a wide expanse of ocean? e. Why are no eutherian (placental) mammals native to Australia?

a. boundary between the pacific and north american plates. they move in 2 different directions b. had not yet collided with eurasia stood alone c. india collided with eurasia d.once apon a time they were connected until plate tectonics started pushing the continents apart e. as the continents drifted apart over the last 200 million years, each became a separate evolutionary arena, with lineages of plants and animals that diverged from those on other continents.

At the end of the last chapter, you were asked about macroevolution. To begin this chapter, give some examples of macroevolution. Include at least one novel example not in your text.

a. emergence of terrestrial vertebrates through series of speciation events b. the impact of mass extinction on biodiversity c. the origin of key adaptations such as flight d. co-evolution (influence of closely associated species on each other in their evolution)

When a structure that has evolved in one context becomes co-opted for another purpose, this event is called ______________________________. Does this imply that organisms are anticipating future needs? __________ Explain.

a. exaptation b. Note that the concept of exaptation does not imply that a structure somehow evolves in anticipation of future use. Natural selection cannot predict the future; it can only improve a structure in the context of its current utility

Figure 25.5 in your text illustrates four different types of fossils. List them here and give an example of an organism that has been preserved in each way.

a. sedimentary rock plant fossil, about 300 million years ago b. mineralized organic matter, petrified tree in arizona about 215 million years old c. trace fossils: 150 million year old dinosaur tracks in colorado d. amber: insects in amber, about 40 million years old e. frozen soil,ice,acid bogs: a 50,000 year old wolf pup found in frozen soil in yukon canada

What properties of life do protocell vesicles demonstrate? What volcanic condition contributes to their formation? (Notice the difference in the graph in Figure 25.4 in your text.)

all organisms must be able to carry out both reproductive & energy processing (metabolism). protocells are abiotic precursors of a living cell that had a membrane like structure & that maintained an internal chemistry different from its surroundings. Adding montmorillonite (soft clay mineral) produced by weathering volcanic ash, increases the rate of vesicle self-assembly. this clay is thought to be common on early earth. provides surface on which organic molecules become concentrated increasing the likelihood that molecules will react with each other & form vesicles.

Does an evolutionary trend imply that there is an intrinsic drive toward a particular phenotype? _________ Explain

an evolutionary trend does not imply that there is some intrinsic drive toward a particular phenotype. Evolution is the result of the interactions between organisms and their current environments; if environmental conditions change, an evolutionary trend may cease or even reverse itself.

Explain how heterochrony, an evolutionary change in the rate or timing of developmental events, can lead to new forms on which evolution can act. Give a human example of this phenomenon.

an organism's shape depends in part on the relative growth rates of different body parts during development. Changes to these rates can alter the adult form substantially, as seen in the contrasting shapes of human and chimpanzee skulls

What group of animals colonized land about 450 million years ago?

arthropods

What unique ability originated with cyanobacteria? How did this alter life on Earth and lead to a wave of mass extinctions?

cyanobacteria first evolved oxygenic photosynthesis. accumulating O2 propably doomed many prokaryotic groups by attacking chemical bonds & damaging cells

Figure 25.29 in your text shows five different types of eyes. How does this support the concept heading that "evolution is not goal oriented?"

every species has a set of eyes that work the best for them. if evolution was goal oriented everyone would have the same eyes. Evidence of their independent evolution can be found in their structure

What other life form appears to have colonized land associated with plants?

fungi

What environmental factors have scientists worried about the potential for a sixth mass extinction?

human actions, such as habitat destruction, are modifying the global environment to such an extent that many species are threatened with extinction.

The most abundant and dominant groups of organisms have changed over time. Some groups rise and others fall. If a group is rising (such as the mammals after extinction of the dinosaurs) what can you say about its extinction rate compared to its speciation rate?

its speciation rate is higher than its extinction rate. the rise of a group happens when there is more speciation compared to extinction

In the previous chart, the first stage is the synthesis of organic molecules. Consider the early planet, which was probably thick with water vapor and stinky with methane, ammonia, and hydrogen sulfide. What gas was missing from this early mix? Why?

no significant levels of oxygen gas were a part of the earths early atmosphere. oxygen would not accumulate in the atmosphere in significant quantities until after the evolution of modern photosynthesis

What effect did the Cambrian explosion have on changing the ways animals obtained their food? How did this affect the number of animal species?

prior to the cambrian explosion animals were not predators they were grazers feeding on algae, fliter feeders, or scavengers. after the explosion animals with claws and other predatory features emerged to capture prey. animal species increased and they got larger

What two areas of biology are merged in the field of study commonly called evo-devo?

research at the interface between evolutionary biology and developmental biology

Everyone's favorite group, the dinosaurs, was lost, along with more than half of all marine species, in a second important mass extinction, the Cretaceous mass extinction, which occurred about 65 mya. What caused it?

researchers proposed that this clay is fallout from a huge cloud of debris that billowed into the atmosphere when an asteroid collided with Earth. One clue to a possible cause of the Cretaceous mass extinction is a thin layer of clay enriched in iridium that dates to the time of the mass extinction. Iridium is an element that is very rare on Earth but common in many of the meteorites and other extraterrestrial objects that occasionally fall to Earth.

Which type of rock is the richest source of fossils?

sedimentary rock

Homeotic genes are master regulatory genes that determine the location and organization of body parts. Mutations in a homeotic gene can have a profound effect on morphology. Homeotic gene mutations can contribute to the potential for evolutionary change. The Hox genes are one class of homeotic genes. What do they control?

the Hox genes, provide positional information in an animal embryo.This information prompts cells to develop into structures appropriate for a particular location.

If you have not studied geology, you will find this concept introduces a fascinating look at the changes in our planet. Continental drift is occurring today as in the past. This is a result of plate tectonics. Explain how these land masses are being moved.

the continents are part of great plates of Earth's crust that essentially float on the hot, underlying portion of the mantle (Figure 25.15). Movements in the mantle cause the plates to move over time in a process called continental drift

Recall that oxidation strips electrons from molecules. A. I. Oparin and J. B. S. Haldane hypothesized that the early atmosphere was a reducing environment. Why is that important? What did they suggest was the source of energy for early organic synthesis?

the early earth atmosphere had no free molecular oxygen, so it was a reducing atmosphere. The source of energy was lightening and UV radiation

The order of fossils deposited in rock strata tell us the sequence in which the fossils were deposited, but what do we NOT know from analyzing rock strata?

the exact age of the fossils

What is the age range for which carbon-14 dating may be used?

up to 75,000 years, any older they contain to little carbon 14

Why did large-scale adaptive radiations occur after each mass extinction?

when survivors became adapted to the many vacant ecological niches.