Unit 3 Test Flashcards
Which part of the gastrula embryo develops into the gastrovascular cavity? What kind of animal would have a gastrovascular cavity as an adult? (2)
- Gastrula invaginates into blastopore.
- Cnidaria and Platyhelminthes (flatworms).
How did the evolution of a septum separating the left and right sides of the heart’s ventricle benefit the fitness of the animals that underwent this change? (4)
- prevented mixing of deoxygenated from oxygenated blood
- provides a higher concentration of oxygen to working muscles
- allowing for stronger muscular contractions
- more work to be accomplished by those muscles.
Which animals have complete ventricular septa and which have incomplete/partial septa?
- The crocodilians, birds and mammals with origins some 100 million years apart, however, have a complete ventricular septa
- Modern reptiles don’t have a complete septa, and do not have the capacity for rapid sustained activity.
How did global climate change over the Devonian and into the Carboniferous, and what was the cause? (8)
- In the Devonian period, the world was experiencing super greenhouse climate conditions
- it was very warm, there probably were no ice caps, there was a lot carbon dioxide in the atmosphere (4,000 ppm)
- plant communities expanded onto land to form the first forests, they depleted the carbon dioxide (CO2) that was in the atmosphere
- CO2 levels dropped to 400 ppm toward the end of the Devonian, it got colder
- There were glaciation events and the rapid change in the climate caused severe extinction in the tropics and the existing coral reefs became extinct.
- the world’s current CO2 level is very close to 400 ppm.
- in the Devonian period, North America and Europe were very close to each other
- During the carboniferous period, massive amounts of photosynthesis removed CO2 from the atmosphere leading to an ice age
How is the hemoglobin in human fetal blood is different from that in the blood of adults? (3)
- The affinity curve of hemoglobin (adult vs. fetal), for oxygen shows in low oxygen conditions likely found in the uterus that fetal hemoglobin will grab onto oxygen from the mother.
- The different structures of hemoglobin mean that it will more or less strongly attract oxygen at the conditions that the organism most needs for it to grab onto the oxygen.
- For human adults, the atmospheric concentration of oxygen is much higher than in the uterus so that adult hemoglobin does not have as strong an affinity for oxygen as the fetus.
What are Hox genes generally, and what is special about those genes specifically identified as the Hox cluster genes? What is the “colinear organization” of these Hox genes? (7)
- Homeobox genes are a large group of similar genes that direct the formation of many body structures during early embryonic development.
- In humans, the homeobox gene group contains an estimated 235 functional genes and 65 pseudogenes (structurally similar genes that do not provide instructions for making proteins).
- These genes are characterized by identifiable promoters called homeobox promoters.
- The sequence order of these genes along a chromosome mirrors the order in which they determine which body parts are coded at which segments of the adult organism.
- Hox genes are arranged in clusters
- their order on the chromosome is the same as the order in which they appear along the body.
- the genes on the left control patterning in the head, and the genes on the right control patterning in the tail.
Briefly describe the anatomy of the avian respiratory system, and explain its advantages relative to the mammalian respiratory tree. (3)
- the exchange occurs in a system of tubes located between an anterior and posterior air sacs, in which the concentration of oxygen is the same as the atmosphere (19-21%)
- with one way passage of air from the posterior air sac, through the exchange tissue (lungs) to the anterior air sac.
- air can pass through the lungs, from the posterior to the anterior air sacs, means that birds have a more efficient respiratory system and can generate enough force to fly
How does the mammalian kidney respond to dehydration? (3)
- The kidneys can adjust the concentration of the urine to reflect the body’s water needs, conserving water if the body is dehydrated or making urine more dilute to expel excess water when necessary.
- ADH is a hormone that helps the body to retain water by increasing water re-absorption by the kidneys.
- conserve water, aquaporins are inserted into the basolateral plasma membrane.
What is the relationship between the diet of an animal and the amount of nitrogenous waste that it produces? Why is a bird better suited for elimination of nitrogenous waste without losing a lot of water, relative to a mammal? (6)
- the higher the nitrogen content in an animal’s diet, the greater amount of nitrogenous waste is produced, often in the form of urea (humans), or uric acid (chickens).
- Meat has a relatively high protein content.
- Proteins are composed of amino acids with a high nitrogen content.
- a carnivorous animal has much higher nitrogen waste content than an herbivore.
- in an amniotic egg, the urea may reach high concentrations toxic to the developing embryo.
- Uric acid, on the other hand precipitates out of solution, and thus embryos inside amniotic eggs can excrete uric acid, accumulate at the bottom of the egg, without polluting the “internal pond”.
What is the anatomical difference between a synapsid and a diapsid? Into what animals did each of these evolve? (2)
- Synapsids are a class of animals that includes mammals and everything more closely related to mammals than to reptiles and birds; have single skull opening (called the temporal fenestra) behind each eye.
- Diapsids are a group of reptiles that developed two holes on each side of their skulls.
What animals gave rise to the sponges? (4)
- single-celled choanoflagellates resemble the choanocyte cells of sponges which are used to drive their water flow systems and capture most of their food
- early studies suggest sponges are the sister group to the rest of animals
- sponges do not form a monophyletic group, in other words, do not include all and only the descendants of a common ancestor
- recent phylogenetic analyses suggest that comb jellies rather than sponges are the sister group to the rest of animals
What group of animals based on overall species diversity, biomass, and the number of individuals is the most successful?
Ecdysozoans, which include the arthropods and nemotoda, are the most successful group based on overall species diversity, biomass, and numbers of individuals, and include insects and crustaceans.
What is the hypothesis for the evolution of jaws? From what did they differentiate? (10)
- Jaws probably originated in the pharyngeal arches supporting the gills of jawless fish.
- The earliest jaws appeared in now extinct placoderms and spiny sharks during the Silurian, about 430 million years ago.
- The original selective advantage offered by the jaw was probably not related to feeding, but to increased respiration efficiency
- the jaws were used in the buccal pump to pump water across the gills.
- The familiar use of jaws for feeding would then have developed as a secondary function before becoming the primary function in many vertebrates
- All vertebrate jaws, including the human jaw, evolved from early fish jaws.
- The appearance of the early vertebrate jaw has been described as “perhaps the most profound and radical evolutionary step in the vertebrate history”.
- Fish without jaws had more difficulty surviving than fish with jaws, and most jawless fish became extinct.
- Jaws originated from gill arches of the fishes, the cartilaginous supports between the gill openings.
- if the anterior gill arches moved forward, and hardened, they could easily evolve into the supports for the jaws.
What is brown fat, and how is its metabolism different from white fat? (5)
Where do you typically find brown fat? (4)
- is a special type of body fat that is turned on (activated) when you get cold
- produces heat to help maintain your body temperature in cold conditions.
- contains many more mitochondria than does white fat (these mitochondria are the “engines” in brown fat that burn calories to produce heat)
- it appears to be able to use regular body fat as fuel
- exercise may stimulate hormones that activate brown fat
- found in highly vascularized deposits in somewhat consistent anatomical locations, such as between the shoulder blades, surrounding the kidneys, the neck, and along the spinal cord
Briefly identify and describe 3 synapomorphies of the Chordata
- notochord: a flexible rod like structure that forms the main support of the body in the lowest chordates; a primitive spine
- nerve cord: a dorsal tubular cord of nervous tissue above the notochord of a chordate
- pharyngeal slit: filter-feeding organs found in non-vertebrate chordates (lancelets and tunicates) and hemichordates living in aquatic environments
Into what tissues does the endoderm typically differentiate (3)
- it’s the innermost of the three germ layers
- Cells derived from the endoderm eventually form many of the internal linings of the body, including the lining of most of the gastrointestinal tract, lungs, liver, pancreas and other glands that open into the gastrointestinal tract, and certain other organs, such as the upper urogenital tract and female vagina.
- Endoderm cells give rise to certain organs, among them the colon, stomach, intestines, lungs, liver, and the pancreas.
Into what tissues does the ectoderm typically differentiate (2)
- forms certain “outer linings” of the body, including the epidermis (outermost skin layer) and hair
- is the precursor to mammary glands and the central and peripheral nervous systems
Into what tissues does the mesoderm typically differentiate (4)
- is the germ layer that distinguishes evolutionary higher life-forms (those with bilateral symmetry) from lower life-forms (those with radial body symmetry)
- allows more highly evolved organisms to have an internal body cavity that houses
- protects organs, bathing them in fluids and supporting them with connective tissue
- Cells derived from the mesoderm, which lies between the endoderm and ectoderm, give rise to all other tissues of the body, including the dermis of the skin, the heart, the muscle system, urogenital system, the bones, and the bone marrow (and therefore the blood)
What are the Reptiliomorpha? What are their distinguishing features? (5)
- Reptiliomorpha is a clade containing the amniotes and those tetrapods that share a more recent common ancestor with amniotes than with living amphibians (lissamphibians)
- two post-orbital fenestrae on either side of their skulls.
- skull loosely attacked to cheek
- tabular large and attacked to parietal
- well developed limbs
- 5 digits
