Biodiversity in Crisis Quiz 2

Describe how we use the layering pattern of rocks, fossils that appear in them, and radiometric dating (explaining what that is) to help us date events in the earth’s history.

Rocks form layers over time, with the older rock layers at the bottom. Fossils of similar organisms are found widely separated on earth. This helps us know which layers are from the same time period in different locations. We can determine the date those organisms lived using radiometric dating. This involves looking at how different the ratio of isotopes of a given element is that would have been expected for an organism living or forming at that time, in which it would have exchanged material with the environment and achieved a ratio similar to the environment at that time. After the death of the organism or burial of the material, decay of the radioactive isotope of an element in the material begins, and its known half-life, plus its measured ratio relative to the stable form of the element, can be used to surmise how long ago the organism died or the material was buried.

Describe the influence that continental drift can have on the earth’s physical environment and biota. Give two examples of times when it played a key role in influencing these.

Continents drift on the earth’s surface over time. Their positions affect ocean circulation, global climate, and sea levels, all factors that can have important influences on the earth’s biota. Also, the meeting of continental plates or meeting of a continental plate and ocean plate can lead to the formation of high or coastal mountains, which also have important influences on what biota can live there. These meetings also (along the way to the formation of mountains) form volcanoes that spew material into the earth’s atmosphere and this can influence the earth’s climate.

 Describe the influence that volcanoes can have on the earth’s physical environment and biota. Give two examples of times when they played a key role in influencing these.

Volcanoes can spew materials into the earth’s atmosphere (ash, roch, SO2) that create a “parasol effect,” blocking some of the sunlight from reaching the surface of the earth, and causing global temperatures to drop. Even a single large volcano has been known to cause a drop of 0.5 degrees Fahrenheit.

Describe the influence that meteorites can have on the earth’s physical environment and biota. Describe two examples of times when they played a key role in influencing these.

The initial explosion from a large meteorite can itself wipe out a great deal of biota. In addition, the debris it throws up into orbit around the earth, that then falls back into the atmosphere and heat the earth up. Also, that smaller debris can block the sun, limiting the photosynthesis that can occur which can have effects up the food chain.

Examples: meteorites effect on the earth during the Hadean, during which the earth was bombarded from space and kept molten. Another is the well known event when a meteorite is thought to have played a key role in the large extinction event at the end of the Cretaceous that wiped out the dinosaurs and many other things about 65 mya.

Describe how atmospheric O2 concentration has changed over Earth’s history and what factors have influenced it. Also, state what transitions in the history of life O2 concentration has had an impact on and why. Be sure to include a description of the “Great Oxidation”, including when it was, what caused it, and what it set the stage for.

O2 concentrations were initially quite low in the earth’s atmosphere. That began to change when the first photosynthetic cyanobacteria evolved about 2.5 bya. They released oxygen as a by-product of photosynthesis, in which organisms take in energy from the sun and store it by converting carbon dioxide and water into sugar molecules and oxygen. This was the “Great Oxidation” in which O2 levels in the atmosphere began to rise. This helped set the stage for eukaryotes to do well, as the higher oxygen concentrations in the atmosphere began to rise. Also, in the ocean as a result meant that larger cells (first cells were quite small) could still absorb the oxygen they needed to carry out life processes (the smaller surface area to volume ratio of larger cells makes this more difficult). It also meant that many anaerobic bacteria, for which the higher O2 was actually toxic, died off. Eukaryotes then also eventually developed the capability to photosynthesize, further increasing oxygen levels. This continued increase in O2 levels set the stage for the success of multicellular organisms, who also are larger and face this challenge of absorbing necessary oxygen through their surface. The evolution of photosynthetic life on land in the form of vascular plants about 350 mya then caused a further dramatic increase in O2 levels in the atmosphere. They were living in swampy environments and their dead material was being buried rather than decomposed. As a result they were producing much more O2 than was being used (none was being used to decompose their dead material). This caused O2 levels to rise to 50% higher than today, and allowed for the age of giant flying insects, who needed higher O2 levels to survive. Eventually, however, the swamps dried up, and O2 levels dropped as some of the dead organic material then became exposed and decayed. The giant insect went extinct. Since that time, O2 levels gradually increased again to where they are today, perhaps in part due to the evolution and success of flowering plants.

Changes in sea level have occurred around the time of each prior mass extinction event. What direction of change in sea level preceded each event (a drop or rise)?

Sea level dropped before mass extinction events. This causes a dying off bc a great deal of marine diversity exists in coastal areas, and those become less in area during sea level drops. Also some of these sea level drops are associated with cooling and great ice sheets (the sea level dropped bc the water cycle was interrupted with water being stuck on land in the form of ice) and these cooling events and ice sheets also caused a good deal of extinction.

State the approximate timing of, and what is meant by the “Age of Giant Insects”. Also state what key environmental condition is thought to have led to it.

The “Age of Giant Insects” is a time when insects were quite large (some as large as humans). It was due to high O2 levels in the atmosphere. (insects don’t have veins in their body that carry oxygen through it like most animals do, so they depend on more diffusion from their body surface to get the O2 they need). 350 mya

As you move from RIGHT TO LEFT on a phylogenetic tree in which the tips are extant (surviving) species, what quantity is increasing?

The amount of time before the present, i.e. how long ago the evolutionary branching occurred.

When using a set of traits to construct a phylogenetic tree, one assumes that species that share a trait (like having fur versus not) are more likely to have a common ancestry. Typically, we use a number of different traits to try to estimate the phylogenetic tree. Two different traits may give us different ideas about what the phylogenetic tree might look like. Describe what principle we use to choose our best estimate of the phylogenetic tree in that case.

Biologists use the principle of “parsimony” to construct phylogenetic trees. They assume the most likely tree is the one with the fewest instances of convergent evolution of a trait (i.e. two species having the same trait even though they are unrelated), and the fewest evolutionary reversals of traits.

simplest answer might be the right answer

Define what a “monophyletic” group is. Be able to determine whether or not a group of organisms on a phylogenetic tree constitutes a monophyletic group.

A monophyletic group contains the common ancestor and all of its descendants. Review the example we went over in class to help you be ready to pick one out on a phylogenetic tree. ***

State the age of the Universe. Describe what happened in the Universe within the first minutes, within the first hundreds of thousands of years, and within 1 billion years.

The universe began with a “Big Bang” 14 billion year ago. In the first minutes protons and neutrons combined to make the first nuclei. In the first hundreds of thousands of years nuclei combined with electrons to create atoms. In the first 1 billion years the universe expanded and cooled, matter attracted matter, creating areas of density, and eventually stars, galaxies, galaxy clusters, etc arose, i.e. the universe developed the kinds of structures we see in it today.

State the age of the Solar System and of Earth.

The solar system and earth are about 4.5 billion years old.

Describe what Earth was like during the Hadean (it’s first 0.5 billion years) and what implications this has for the History of Life during this time.

During the hadean, the earth was still being bombarded by materials from space and was kept molten by these constant explosions.

Describe what changes in the Earth’s physical environment occurred as it approached and moved into the Archaean that made it more hospitable to the origin of life.

The earth eventually cooled down bc the bombardment by materials lessened greatly (much of the material in the solar system had become planets). It also began to form an atmosphere, which protected it from some of this bombardment (things would disintegrate in the atmosphere before hitting the earth’s surface). As the earth cooled, it formed a crust and began to sustain water molecules.

What key molecule is thought to have originated first as a precursor to life, before actual “life” occurred?

RNA, the molecules cells currently use to transport genetic information from the DNA to the rest of the cell and also used in the synthesis of proteins. Since RNA can both replicate and synthesize proteins, it was thought to have come first.

Describe what the Miller-Urey experiment shows us is possible to have occurred.

The Millar-Urey experiment replicated early earth conditions and elements available, and showed it can result in the spontaneous formation of sugars and amino acids (the building blocks of proteins and RNA).

State 3 key differences between prokaryotes and eukaryotes. Also, answer, are prokaryotes a monophyletic group?

Prokaryotes are smaller, they carry out a more efficient form of cell division called fission, they lack a nucleus and mitochondria. Prokaryotes are not a monophyletic group because eukaryotes descended from archaea, who are prokaryotes.

A key difference between archaea and bacteria is that the latter have a substance called peptidoglycan in their cell wall. Gram + and gram – bacteria vary in the amount of peptidoglycan they have, with gram + having substantially more. Why is peptidoglycan is significant for human health concerns with bacteria?

The antibiotics we use to fight infection exploit peptidoglycan to attack bacteria and kill them.

Describe the key steps that occurred in the evolution eukaryotes from the prokaryotic cell form of archaea.

Ancient prokaryotes that eukaryotes evolved from has cell walls, and the eukaryotes lost that forming a flexible cell surface which allows for enfolds and hence greater surface to volume ratio. Also, eukaryotes developed a nucleus which enfolded membrane may have developed into nuclear membrane around DNA. Additionally, eukaryotes acquired mitochondria from endosymbiosis by an archaea of a protobacterium (one of bacterial lineages capable of aerobic respiration).

What key process is carried out in eukaryotic cells in their mitochondria? What are its inputs and outputs? (Be able to provide the name of the process, and provide in words the inputs and outputs of the chemical reaction.)

Mitochondria are now used for respiration, the breaking down of molecules storing energy to release that energy. Sugar and oxygen combine, energy is released, and water and carbon dioxide are the end products.

Provide the names of the major groups of eukaryotes we defined in class. When did these major groups of eukaryotes arise? Be able to provide both the approximate number of years ago, and the name of that time we used that is based on the key geologic era it predated.

Plants, Animals, Fungi, Protists. They all arose in the pre-Cambrian, about 1-1.5 bya.

What is the “Cambrian Explosion”? When did it occur?

The explosive diversification of multicellular eukaryotic life form, in particular marine animal forms, that occurred starting around 500 mya in the first Era, the Cambrian Era, of the Paleozoic.

What shared derived characteristic do all members of Plantae have?

They all descended from a lineage in which primary endosymbiosis occurred, in other words a lineage of a eukaryote (it had already obtained a mitochondria through endosymbiosis) that engulfed a photosynthesizing cyanobacteria.

Describe the key reaction of photosynthesis in words, identifying its key inputs and key outputs.

Energy it harnesses to convert carbon dioxide and water into sugar and oxygen is released.

State some example organisms we discussed in class that evolved from non-photosynthetic eukaryotes through secondary endosymbiosis. Describe what secondary endosymbiosis is.

Diatoms and dinoflagellates. The former are a significant component of phytoplankton communities and carry out 20% of the photosynthetic carbon fixation on our planet. The latter are the photosynthesizing eukaryotes that have a symbiotic association with reef building coral animals. They obtain CO2 and shelter from the coral animals and provide it with its food. Secondary endosymbiosis was when a non-photosynthesizing eukaryote engulfed a chloroplast-containing eukaryotic cell and formed a symbiotic association with it.

State and describe what adaptations/evolutionary transitions allowed plants to be widely successful on land.

The evolution of maternal tissue protecting their developing embryos enabled their offspring to develop outside of water, vascular tissue then enabled them to be successful in drier conditions, since it allowed them to transport water from area where it is present in the soil to their leaves where it is needed for photosynthesis, then seeds provided further protection and nutrients to the developing embryo and encouragement of animal dispersal.

Approximately when did grasses evolve and become widespread? What key innovation they evolved is thought to have contributed to their success?

Grasses evolved around 100 mya and became dominant more like 50-65 mya, after the dinosaurs went extinct. It is thought that their evolution of C4 photosynthesis is more efficient in hotter, drier climates and there was a period of warming around that time.

Why are grasses especially important to humans?

Humans use some grass species (e.g. wheat, corn, rice) for agriculture and this helped create stable human civilizations.

State the four key traits of animals we highlighted in class.

Multicellularity, heterotrophy, internal digestion, movement and nervous system

A key monophyletic group of animals we highlighted, which contains Ecdysozoans (which contains Arthropods), as well as Chordates (which contain Vertebrates) is Bilaterians. What key characteristic to Bilaterians have?

Bilateral symmetry in their bodies

Reef-building coral are animals. Are they Bilaterians?

No. ***** be able to discern that if given the phylogeny of animal evolution we looked at in class if told they are part of the cnidarians. Be able to identify what shared-derived characteristics of bilaterians they do not share.

What key taxonomic group within animals did we emphasize in class contains > ½ of the described species?

Arthropods

What key characteristics define Arthropods?

Exoskeletons that molt, segmented bodies, paired joints

What example Arthropod is especially important to human agriculture?

European honeybee is used to pollinate many crops.

All vertebrates evolved from a bony fish lineage that survived the Devonian mass extinction. Describe the three major transitions we mentioned in the evolution or organisms from this bony fish form to “Amniotes” that live their entire lives on land.

The bony fish lineage evolved into lung fish that could breathe air when surfacing, and then into amphibians (their 4 fins evolved into 4 limbs and they became tetrapods), then those tetrapods evolved amniotic eggs, allowing them to reproduce on land.

Describe the Fungal Infection Mammalian Selection (FIMS) hypothesis for why mammals evolved to fill niches previously occupied by the dinosaurs after they went extinct. (We watched a video about this topic.)

This hypothesis is that the time right after the meteorite that killed dinosaurs, in which there was quite a bit of dead material and little light, was especially good for fungi, and that they infected potential reptiles that might have filled the niches left empty by dinosaurs more easily than they infected mammals which are warm-blooded, so the mammals ended up being the successful ones that filled in those empty niches.

What are the shared characteristics of mammals? What are some of the advantages these traits provide? Note that an alternative hypothesis to FIMS is just that mammals simply managed to survive the event that cause the Dinosaurs to go extinct, and were well-adapted to their niches with these traits and hence just set up well for their future success.

Their bone structure in their head especially related to their hearing and jaws, and that they produce milk for their young ****** need to write down the advantages