Zoology Unit 5 Homework Questions
Terms in this set (65)
List four functions of the integumentary system.
-consists of skin, hair, nails, glands, nerves
-acts as barrier to protect body
-retain body fluids, protect against disease, eliminate waste products, regulate body temp
-ultimately helps maintain homeostasis by working w/ other body systems
What is difference between structural colors and colors based on pigments? How do the chromatophores of vertebrates and cephalopod molluscs differ in structure and function?
-structural colors- physical structures reflect wavelength of light back and provide colors at different angles
-pigment colors - chemically absorb wavelengths and reflect back one color
-vertebrates- pigments in large cells w/ branching processes called chromatophores. Can be in middle of cell or dispersed to change visability
-Cephalopod molluscs - each chromatophore is in a sac like cell filled w/ pigment granules and surround muscle cells that when contracted, stretch the whole cell into a pigmented sheet and shrink to a small sphere when muscles relax
As "naked apes" humans lack the protective investment of fur the shields other mammals from the damaging effects of sunlight. How does human skin respond to ultraviolet radiation in the short term and with continued exposure?
-Melanin works as UV absorbent
-Short doses of exposure to melanin in skin = increased causing tan effect
-prolonged exposure = damage to skin such as sun burns and extreme exposure = skin cancer
What is keratin? What is the most abundant protein in metazoans? An animal fibrous protein that is exported by exocytosis and assembled into fibers.
-Keratin = fibrous protein forming main structural components of hair, feathers, hoofs, etc.
-Collagen = major insoluble fibrous protein in the extra cellular matrix and connective tissue
Distinguish between epidermis and dermis in vertebrate integument, and describe structural derivatives of these two layers.
-skin has two major layers-
1. outer thin epidermis consists of closely packed cells with inter cellular material, providing a barrier against attacks by chemicals, radiation, etc.
2. underlying dermis is thicker and tougher and is formed by extra cellular materials manufactured by scattered cells. Provides physical protection.
-The sensory structures such as scales, feathers, claws, etc. are derived from either the dermis, epidermis, or both
A "9 + 2" arrangement of microtubules is typical for both cilia and flagella. Explain how this system is thought to function to produce a bending motion. What is the difference between a cilium and a flagellum?
-functions by a series of microtubule-associated proteins (MAPs) that connect microtubule doublets to each other and to central pair of microtubules, and it is the structural support that makes cilia and flagella movement possible
-a flagellum is longer and beats symmetrically with snake-like undulations
-a cilium is shorter and beats asymmetrically with strokes single moving up and down
One of the special qualities of vertebrate bone is that it is a living tissue that permits continuous remodeling. Explain how the structure of bone allows this remodeling to happen.
-Compact bone = calcified bone matrix arrange in concentric rings. Between these rings are cavities (lacunae) containing osteocytes (bone cells) that extend through many passages (canaliculi).
-These processes interconnect bone cells and allow communication between them and serve to distribute nutrients and growth factors throughout the bone
What is the difference between endochondral and membranous bone?
-endochondral = long, short, irregular; develops cartilage
membranous = flat; develops directly from sheets of embryonic cells
During evolution, skeletal muscle became adapted to functional demands ranging from sudden, withdrawal movements of a startled worm, to the sustained contractions required to maintain mammalian posture, to supporting a long, fast chase across the African savanna. What are some of the fiber types in vertebrate muscle that evolved to support these kinds of activities?
Slow oxidative Fibers- specialized for slow sustained contractions without fatigue, important in maintaining posture.
Fast glyotic fibers- function anaerobically, fatigue rapidly, used for running.
Fast oxidative Fibers- extensive blood supply with a high density of mitochondria, function aerobically used for rapid sustained activities.
Name the basic classes of foods that serve mainly as (a) fuels and as (b) structural and functional components.
-Proteins, Water, Mineral Salts, and Vitamins
Distinguish between the following pairs of terms: autotrophic and heterotrophic, phototrophic and chemotrophic, microphageous and macrophageous, suspension feeding and deposit feeding, herbivores and carnivores, omnivores and insectivores.
Autotrophic-makes organic nutrients from inorganic raw materials
Heterotrophic- must obtain both organic and inorganic raw materials from environment in order to live
Phototrophic- capable of using CO2 in presence of light as a source of metabolic energy.
Chemotrophic- organism that derives nourishment from inorganic substances without chlorophyll
Explain the characteristics, advantages, and limitations of suspension-feeding, and name three different groups of animals that are suspension feeders.
suspension feeding- feeding on small, suspended food in water
-characteristics such as ciliated surface or mucus sheets that draw food particles in to mouths
-advantages = many suspension feeders do not have to move to find food
-limitations- supply of food particles like plankton aren't evenl distributed- can be hard to locate food
-ex. polychaete worms, bivalve molluscs, hemichordates
Compare intracellular and extracellular digestion and suggest why there has been a phylogenetic trend in some animals from intracellular to extracellular digestion.
-Intracellular digestion- occurring within a body cell or within body cells
-Extracellular digestion- secrete enzymes through cell membrane onto food
-With evolution of greater complexity and appearance of complete mouth-to-anus alimentary systems, extracellular digestion became more emphasized.
Which structural modifications vastly increase the internal surface area of the intestine (both vertebrate and invertebrate) and why is the large surface area important?
-structural modifications like accordion-like pleats and millions of tiny hair-like protrusions, villi, line and increase the surface area of the inside of the small intestine.
-Large surface area is important b/c more room for glands to release digestive enzymes, and maximizes absorption of nutrients into bloodstream
Briefly describe the sequence of events that leads to blood coagulation.
In vertebrates, blood coagulation occurs as a complex series of chemical reactions that produce a tangled network of fibers form one of the plasma proteins, fibrinogen. The enzyme thrombin catalyzes the transformation of fribrinogen into a fibrin meshwork that entangles blood cells to form a gel-like clot. Thrombin is normally present in blood in an inactive form called prothrombin, which must be activated for coagulation to occur.
Two distinctly different styles of circulatory systems have evolved among animals: open and closed. What is "open" about an open circulatory system? Closed systems sometimes are cited as adaptive for actively moving animals with (at least at times) high metabolic demand. Can you suggest possible reasons for this assertion?
-open= don't contain system of veins, arteries, or vessels to transport blood and oxygen in organs, but instead blood covers surface and surrounds all of the organs and tissues and blood/oxygen delivered that way
- closed systems are adaptive for moving animals possibly because it provides a constant supply of oxygen and glucose to the organisms muscles
Describe the tracheal system of insects. What is the advantage of such a system for a small animal?
-air enters tracheae by pores called spiracles which are located on sides of insects abdomen
-oxygen taken directly to tissue that needs it
-advantage b/c small insects don't need a full tracheal system
What is the advantage of a fish's gills for breathing in water and a disadvantage for breathing on land?
-advantage= fish's gills are dissolved oxygen in water at lower concentration of oxygen
-disadvantage= very high concentration of oxygen, so it's not usable for fish
The ability of hemoglobin to bind oxygen decreases with decreasing oxygen concentration and also decreases with increasing carbon dioxide concentration. What effect do these phenomena have on the delivery of oxygen to tissues?
This phenomena doesn't allow sufficient oxygen to be supplied to the cells in muscles and tissues b/c hemoglobin cannot bind to the oxygen. This deprivation eventually leads to the inhibition of cells to undergo aerobic respiration and forces them to revert to anaerobic respiration, resulting in a buildup of lactic acid which brings about muscle soreness.
-no sufficient oxygen supplied to cells in muscle tissue
-hemoglobin can't bind to oxygen
-leads to inhibition of cells to do anaerobic respiration
-buildup of lactic acid = muscle soreness
Provide a brief description of the lymphatic system. What are its principle functions? Why is movement of lymph through the lymphatic system very slow?
1. series of vessels throughout body that drain fluid from tissues
2. collects and transports fluid, returns plasma proteins to bloodstream, absorbs digested fats, builds immunity to infection diseases
-movement is slow because there aren't lymphatic pumps and lymph is propelled by action of the nearby skeletal muscles.
Trace the flow of blood through the heart of a mammal, naming the four chambers, their valves, and explaining where the blood entering each atrium comes from and where the blood leaving each ventricle goes. When the ventricle contracts, what prevents blood from reentering the atria? What factors cause blood to move forward at high pressure in the atria?
All blood enters the right side of the heart through two veins: the superior Vena Cava (SVC) and the Inferior Vena Cava (IVC). The SVC collects blood from the upper half of the body, the IVC collects blood from the lower half of the body. Blood leaves the SVC and the IVC and enters the right atrium (RA). When the RA contracts the blood goes through the tricupsid valve and into the right ventricle (RV). When the RV contracts blood is pumped through the pulmonary valve into the pulmonary artery (PA) and into the lungs where it picks up oxygen. Blood returns to the heart from the lungs by the pulmonary veins and goes into the left atrium (LA). When the LA contracts blood travels through the chamber mitral valve and into the left ventricle(LV). The LV is an important chamber that pumps blood through the aortic valve and into the aorta. The valves close and only work one way which prevents blood from re-entering the atria. Factors that can cause blood to move at a high pressure are smoking, obesity, lack of physical activity, stress, and older age.
Relate the function of contractile vacuoles to the following experimental observations: to expel an amount of fluid equal in volume to the volume of the animal required 4 to 53 minutes for some freshwater protozoa, and between 2 and 5 hours for some marine species.
-contractile vacuole eliminates fluid and at certain salinity will cease to function
-marine animals thrive in environments with high salt concentration, making the vacuole work at slower pace than that of a freshwater protozoa
In what animals would you expect to find a salt gland? What is its function?
-the salt gland is an organ for excreting excess salts
-found in sharks, rays, skates, seabirds, and some reptiles.
What strategy does a kangaroo rat use that allows it to exist in the desert without drinking any water?
-the Kangaroo Rat produces the most concentrated urine and only passes a few drops per day
-such high concentration means the Kangaroo Rat loses little water in it's urine.
Distinguish the terms in the following pairs: osmotic conformity and osmotic regulation; stenohaline and euryhaline; hyperosmotic and hypoosmotic. Most marine invertebrates are osmotic conformers. How does their body fluid differ from that of sharks and rays, which are also in near osmotic equilibrium with their environment?
Osmotic Conformity: An osmotic conformer is a being that changes its body temperature with its surroundings in order to survive.
Osmotic Regulation: An osmotic regulator does not change its body temperature depending on its surrounding, but rather regulates its body temperature in all environment.
hyperosmotic-higher concentration in organism than environment
Sharks and rays have a kidney that keeps them at a close concentration to seawater, and marine invertebrates do not have a regulatory system and merely just let the water flow through.
The problems of water balance may have arisen when early metazoan animals began to invading estuaries and rivers. Describe the physiological challenges confronting marine invertebrates entering freshwater and, using crustaceans as an example, suggest solutions to these challenges.
-marine invertebrates face physiological problems b/c their body fluids are osmotically more concentrated to the freshwater therefore water flows easily into the animals body through the thin, permeable membranes of the gills. This causes its body fluids to become too dilated
Also, these animals lose salt easily across its gills because of the difference in concentrations. These challenges are compensated for in crustaceans by antennal glands located on the head which excrete excess water or dilute urine and by salt- secreting cells in the gills which actively remove ions from dilute seawater and move them into blood.
How does a protonephridium differ structurally and functionally from a true nephridium (metanephridium)? In what ways are they similar?
Differ- Pro has closed system, meta has open
Pro not vascularized
Similar- urine formation
kidneys operate same way
Why does nitrogenous waste build up in cellular fluids? Discuss the tradeoffs between water loss, energy efficiency and toxicity with the excretion of ammonia, urea, and uric acid. List example organisms for each.
Nitrogenous waste builds up in cells because of metabolic processes and amino acid degradation that produces the waste
-Ammonia: requires a lot of water to flush, requires little energy, and is very toxic ex. fish
-Urea- requires less water to flush, requires little energy, and in less toxic ex. mammals
-Uric acid- requires very little water to flush, requires a great amount of energy and is non toxic- ex. birds
Explain why it is an advantage for certain small birds and mammals to abandon homeothermy during brief or extended periods of their lives.
-Advantage = allows the body temp to face thus showing metabolic processes. Requires less energy which is very helpful during hibernation.
Define homeostasis. What evolutionary advantages for a species might result from successful maintenance of internal homeostasis?
Homeostasis- a tendency to move toward a relatively stable equilibrium between interdependent elements, especially as maintained by physiological processes.
-allows organism to sustain bodily functions in widely varied environmental conditions
What ionic and electrical changes occur during the passage of an action potential along an axon?
As an action potential travels down the axon there is a change in polarity across the membrane the Na+ and K+ gated ion channels open and close at the membrane reaches the threshold potential in response to a signal from another neuron
Describe the microstructure of a chemical synapse. Summarize what happens when an action potential arrives at a synapse.
Chemical synapses include: Synaptic Cells ( junction between presynaptic membrane and postsynaptic membrane)
Synaptic Vesicles (balls containing the neurons)
Ligand ion channel for Na2+ and K+
When action potential arrives at a synapse:
1) membrane of the presynaptic terminal depolarizes, opening voltage-gated Ca2+ channels
2)Influx of Ca2+ into neuron terminal triggers movement of synaptic vessels
3)synaptic vesicles fuse with the membrane, releasing neurotransmitter into the cleft
4) Neurotransmitter diffuses across synaptic cleft
5) Neurotransmitter that contacts a receptor on postsynaptic membrane binds to that receptor
Define the following: neuron, axon, dendrite, myelin sheath, afferent neuron, efferent neuron, association neuron.
a neuron is a specialized cell transmitting nerve impulses; a nerve cell. myelin sheath is the insulating covering that surrounds an axon with multiple spiral layers of myelin. afferent neurons are pathways that carry sensory information from the body to the central nervous system. efferent are conducting cells that carry information from the central nervous system. association neurons are located in the spinal cord and the brain that conduct impulses between other neurons
What are ventral nerve cords with metamerically arranged ganglia and who has them?
-The ventral nerve cord runs along the floor of the coelom to the last segment of the body
-It provides nerves to body structures
-They are found in annelids, like earthworms.
Describe the cnidarian nervous system. How is a tendency toward centralization manifested in flatworms, annelids, molluscs, and arthropods.
- a nerve net covers the body
- composed of interconnected neurons, but with no centralization (no brain)
- all reactinos are reflexes but can be shared with other regions
-flatworms - nerves connected to anterior ganglia
-annelids- segmental ganglia and bilobed brain
-molluscs- a pair of cerebral ganglia
-arthropod- segmental, large ganglia
Name major functions associated with the following brain structures: medulla oblongata, cerebellum, tectum, thalamus, hypothalamus, cerebrum, limbic system.
medulla oblongata- regulates heart rate and force of contraction on the heart
cerebellum- involuntary coordination such as controlling equilibrium and posture
tectum- integrates info from eyes and ears
thalamus- integrates info from all senses
hypothalamus- secretes hormones and controls desires like hunger
cerebrum- controls voluntary muscle movements
limbic system- mediates species - specific behavior that relate to food and sex; memory and spatial learning in the hippocampus
Chemoreception in vertebrates is distinguishable as the distinct senses of smell and taste. Contrast these two senses in human terms of anatomical location and nature of the receptors and sensitivity to chemicals in insects.
taste in insects:
-taste sensilla occur on the mouth parts, legs, and wing margins of insects. In general, taste is more restricted in response and is less sensitive than smell
smell in insects
-olfactory sensilla occur on the head on two pairs of olfactory organs: the antennae and the maxillary palps. Olfaction guides feeding behavior, location, and selection of sexual matter, territorial and trail marking, and alarm reactions of numerous animals.
Define the following and give several examples of each: Chemoreception, Mechanoreception, Photoreception.
chemoreception is The physiological response of a sense organ to a chemical stimulus. Mechanoreception is is a sensory receptor that responds to mechanical pressure or distortion. Photoreception refers to mechanisms of light detection that lead to vision and depends on specialized light-sensitive cells
Explain how ultrasonic detectors of certain nocturnal moths are adapted to help them escape an approaching bat.
Bats emit an ultrasonic blast that radiates out until the sound hits something and it bounces back, letting the bat know that something is in front of them. Moths can detect this sound and are able to tell if bats are around. When the bats are close the sound is high and moths can fly downward and hope to escape.
Contrast the structure and function of the compound eye of arthropods with the camera type eye of cephalopods and vertebrates.
Compound eye of arthropods
-contains ommatidia w/ lens, crystalline cone, varying cells, and optic nerves
-each ommatidia helps insect view small parts of visual field; poor vision but detects motion well
Camera type eye of cephalopods
-lens, pupil, iris, cornea, retina, etc.
-lens bends incoming light to form image on retina-photoreceptor cells absorb incoming light and consist of rods and cones-sends info through optic nerve to brain
What is the importance of feedback systems in the control of hormonal output? Offer an example of hormonal feedback pattern
-importance- maintains homeostasis and ensures body doesn't deviate far away from a setpoint
ex. thyroid hormone- when level drops, TRH released by hypothalamus to the anterior pituitary gland which releases TSH to thyroid gland which releases thyroid hormone which is recepted on most body cells. Causes hypothalamus to end pathway cycle and returns the normal setpoint.
In which invertebrate phyla is endocrine function observed? Which invertebrate phyla possess endocrine glands? Give two examples of invertebrate hormones that regulate metabolism.
Cnidarians, nematodes, and annelids. Endocrine glands are possessed in molluses and arthropods. Crustacean hyperglycaemic hormone, and adipokinetic hormone.
Explain how three hormones involved in insect growth; ecdysone, juvenile hormone, and PTTH, interact in molting and metamorphosis.
ecdysone- molting hormone which gives rise to both larva and the adult, while juvenile hormone retains the juvenile characteristics. PTTH controls the production of ecdysone. During juvenile life, the production of the juvenile hormone is constant, while the molting hormone ecdysone is produced intermittenly by release of PTTH. This produces a molt, which gives size to a larger juvenile. After a required number of juvenile molts, the production of the juvenile hormone decreases. This allows the final molt to transform into an adult with the combined action of ecdysone and PTTH.
Describe the chemical nature and function of two posterior-lobe hormones, oxytocin and vasopressin. What is distinctive about the ways these neurosecretory hormones are secreted compared with the neurosecretory release and release-inhibiting hormones that control the anterior pituitary hormones?
-The two posterior-lobe hormones of mammals, oxytocin and vasopressin, are chemically very much alike. Both are polypeptides consisting of eight amino acids.
-oxytocin- contraction of uterine muscles during childbirth
-vasopressin- acts on kidneys to reabsorb water. Increases blood pressure and sensation to thirst.
-These hormones are among the fastest-acting hormones, since they can produce a response within seconds of their release from the posterior lobe.
Explain the actions of two hormones of the islets of Langerhans on the level of glucose in the blood. What is the consequence of insulin insufficiency or insensitivity as in the disease diabetes mellitus?
-islets secrete the hormones insulin and glucagon which regulate the level of glucose in the blood
-insulin secreted when the blood glucose level rises too high and used to lower it back to normal
-glucagon used when blood glucose level falls too low and is used to rise it back to normal
-consequence of insulin insufficiency as in diabetes mellitus is that insulin isn't produced so the uptake of glucose by cells is not possible, therefore blood cells starve.
-consequence of insulin insensitivity is that while insulin secretion is normal, cells do not take up the glucose, causing the pancreas to increase secretion of insulin until levels are too high
Explain how the female hormones GnRH, FSH, LH, and estrogen interact during the female menstrual cycle to induce ovulation and, subsequently, formation of the corpus luteum. Describe the role of HCG.
The process in which the female hormones GnRH, FSH, LH, and estrogen interact during the menstrual to induce the menstrual cycle and the subsequent formation of the corpus luteum.
-in ovary, primary follicle begins forming to mature follicle (follicular phase)
-day 3, FSH and LH rise in blood; induces follicles to grow and secrete estrogen
-endometria thickens(proliferative phase)
-day 10, only one follicle is left and rest degenerate- Graafian follicle
-day 14- FSH induces G follicle to secrete large amounts of estrogen; induces production of GnRH from hypothalamus
-increases production of LH and FSH from anterior pituitary
-high levels of LH cause G follicle to rupture releasing oocyte
-corpus luteum is formed frim remains of ruptured follicle that releases oocyte at ovulation
-corpus luteum, responding to LH, becomes transitory endocrine gland that secretes progesterone
Define asexual reproduction, and describe four forms of asexual reproduction in invertebrates.
Asexual Reproduction: a type of reproduction by which offspring arise from a single organism, and inherit the genes of that parent only; it does not involve the fusion of gametes and almost never changes the number of chromosomes.
-Binary fission: Binary fission involves mitosis only and hence the resultant individuals are genetically identical to each other and to the parent. The whole parental body acts as the reproductive unit. The nucleus of the unicellular parent organism divides into two. This is followed by the division of the cytoplasm and 2 daughter cells of almost equal size are formed. The daughter cells grow in size and then divide again.
-Multiple fission: In some organisms the nucleus of the parent divides into many daughter nuclei by repeated divisions. This is followed by the division of the cytoplasm into several parts with each part enclosing one nucleus. So a number of daughter cells are formed from a single parent at the same time. This kind of fission is known as multiple fission.
-Budding: divides forming two cells, with potential to regrow to full size of original cell
-Fragmentation: parent breaks into fragments, each capable of growing into independent organism
Define the following: oviparous, ovoviviparous, viviparous, radial and regulative cleavage, mosaic development, deuterostomes, pharyngeal slits, spiral cleavage, blastopore, coelom, archenteron.
Oviparous: producing young by means of eggs that are hatched after they have been laid by the parent.
Ovoviviparous: producing young by means of eggs that are hatched within the body of the parent, as in some snakes
Viviparous: bringing forth live young that have developed inside the body of the parent.
Radial Cleavage:Embryonic development in which early cleavage planes are symmetrical to the polar axis, each blastomere of one tier lying directly above the corresponding blastomere of the next layer; typically occurs with regulative cleavage.
Regulative Cleavage: embryonic development in which the fertilized ovum undergoes indeterminate cleavage, producing blastomeres that have similar developmental potencies and are each capable of giving rise to a single embryo.
Mosaic Development: development characterized by independent differentiation of each part of the embryo; determinate cleavage.
Deuterostomes: a sub taxon of the Bilateria branch of the subkingdom Eumetazoa, within Animalia, and are distinguished from protostomes by their embryonic development.
Pharyngeal Slits: filter-feeding organs found in Invertebrate chordates (lancelets and tunicates) and hemichordates living in aquatic environments.
Spiral Cleavage: holoblastic cleavage that is typical of protostomes and that is characterized by arrangement of the blastomeres of each upper tier over the cell junctions of the next lower tier so that the blastomeres spiral around the pole to pole axis of the embryo
Blastopore: the opening of the central cavity of an embryo in the early stage of development.
Coelom: the body cavity in metazoans, located between the intestinal canal and the body wall.
Archenteron: the rudimentary alimentary cavity of embryo at the gastrula stage.
A paradox of sexual reproduction is that despite being widespread in nature, the question of why it exists at all is still unresolved. What are some disadvantages of sex? What are some consequences of sex that makes it so important?
-disadvantages: slower rate of reproduction, less reliable means of reproduction and takes time and energy to find a mate
-consequences- provides genetic variation and offspring have different parents, making more offspring able to mate
Explain why genetic mutations in asexual organisms lead to much more rapid evolutionary change than do genetic mutations in sexual forms. Why might harmful mutations be more deleterious to asexual organisms compared with sexual organisms?
Because in asexual reproduction all traits including mutations are passed on to the offspring, then from there on those traits are in turned passed on to their offspring. The reason that harmful mutations could be deleterious is because they will not go away, rather they will be passed on until the species dies or adapts to retroact the mutation, this is contrasted with sexual reproduction where the mutation can be weeded out and could possibly go away because it isn't guaranteed that it will be passed on due to genetic variation.
Define two alternatives to bisexual reproduction - hermaphroditism and parthenogenesis - and offer a specific example of each from the animal kingdom. What is the difference between ameiotic and meiotic parthenogenesis?
hermaphroditism- condition of having both male and female organs in same individual ex. earthworms
parthenogenesis- the development of an embryo form an unfertilized egg, or one in which the male and female nuclei fail to unite following fertilization ex. rotifers
-meiotic- asexual; no meiosis occurs and egg formed by mitotic cell division
-meiotic- sexual; haploid ovum is formed by meiosis
Define the terms dioecious and monoecious. Can either of these terms be used to describe a hermaphrodite?
Dioecious: Having male and female gonads in separate individuals.
Monoecious: Having both male and female gonads in the same organism
Monoecious can be used to describe hermaphrodites.
How is an egg (oocyte) prepared during oogenesis for fertilization? Why is this preparation essential to development?
-one obvious feature of egg preparation is the deposition of the yolk.
-important b/c yolk contains materials like proteins and lipids that, after fertilization, are used as nutrition for the sperm
-during prep, cytoplasm accumulates, which is important b/c it comntains elements required for protein synthesis. Also during prep, a jelly layer forms around the egg, which is important bc it prevents polyspermy
In what significant ways does spermatogenesis differ from oogenesis?
spermatogenesis- takes place in testes; produces a far great number of sperm than eggs in oogenesis
oogenesis- takes place in ovaries
Define sexual reproduction and explain why meiosis contributes to one of its great strengths.
Sexual Reproduction: the production of new living organisms by combining genetic information from two individuals of different types (sexes). In most higher organisms, one sex (male) produces a small motile gamete that travels to fuse with a larger stationary gamete produced by the other (female).
It contributes because it causes variation in reproduction which can lead to new evolutionary adaptations that can advance a species.
Describe the events that follow contact of a spermatozoon with an egg. What is polyspermy and how is it prevented?
Sequence of events:
-tip of sperm touches the vitelline envelope of the egg
-fertilization cone formed
-fast block to polyspermy occurs
-fusion of sperm membrane with the egg membrane
-loss of sperm flagella
-cortical reaction occurs
-fertilization membrane established
-sperm migrates towards the center of the egg
-nuclear envelope breaks
-sperm chromatin expands
-fusion of sperm and egg nuclei
-development of zygote
polyspermy- more than one sperm in one egg
-prevented by a transient electrical barrier that forms around the egg and then next by elevating the envelope and lifting away all sperm bound to it, except the one that has successfully fused w the egg membrane.
How does amount of yolk affect cleavage? Compare cleavage in a sea star with that of a bird.
• When yolk is present, cleavage furrows extend completely through the egg in holoblastic cleavage. When large amounts of yolk is present, cleavage is meroblastic, with cells sitting atop a mass of undivided yolk
• The starfish oocyte contains little or no yolk (microlecithal) and divides completely into uniform daughter cells (equal holoblastic cleavage).
• The chick egg contains large amounts of yolk (macrolecithal) and cleavage is restricted to the active cap of cytoplasm (meroblastic cleavage).
What developmental characters are used to divide animals between protostomes and deuterostome clades?
• Protostome -spiral cleavage, mosaic embryo, blastopore becomes mouth and anus forms second, coelom forms by splitting
• Deuterostome -radial cleavage, regulative embryo, blastopore becomes anus, mouth forms second, coelom forms by outpocketing
What is the difference between spiral and radial cleavage?
spiral cleavage- occurs oblique to the animal vegetal axis rather than parallel or perpendicular to the axis like in radial cleavage
-spirally cleaving blastosomes pack themselves tightly together rather than just lightly contacting eachother as do many radially cleaving blastosomes
What is the difference between schizocoelous and enterocoelous origins of a coelom?
-differ from each other by the region of the endoderm where the cells that form the coelom come from
-schizocoelous originate in mesodermal band around the gut
-entercoely cells originate in gut cavity
Which phyla have mesoderm derived from or with the endoderm from enterocoelic pouches.
If identical human twins develop from separate placentas, when must the embryo have separated? When must separation have occurred if the twins share a common placenta but develop within separate amnions?
If the fetuses have two different placenta then separation occurs usually in the first 2 days after fertilization, while if the fetuses share a placenta but have separate amniotic sacs then separation occurs 2 days after fertilization.
What is the embryological evidence that vertebrates form a monophyletic group?
-significant evidence- post gastrula vertebrate embryos and its 5 shared chordate hallmarks are present at about the same stage of development. During this moment, vertebrate embryos are almost interchangeable with eachother
What are the four extraembryonic membranes of amniotic eggs of birds and reptiles and what is the function of each membrane? What is the fate of the four extraembryonic membranes in placental mammals.
Amnion: Innermost layer of the extraembryonic membranes forming a fluid-filled sac around the embryo in amniotes. This serves as a membrane that provides fluid protection.
Allantois: consists of embryonic tissues and helps handle waste and exchange gases
Chorion: outermost!!! forms placenta!!!the outermost membrane surrounding an embryo of a reptile, bird, or mammal. In mammals (including humans), it contributes to the formation of the placenta.
Yolk Sac: nutrients!!! a membranous sac containing yolk attached to the embryos of reptiles and birds and the larvae of some fishes. It provides nutrients to the developing embryo.
What are homeotic genes and what is the "homeobox" contained in such genes? What is the function of the homeobox? What are Hox genes? What is the significance of their apparently universal occurrence in animals?
-homeotic genes- segment specific genes that regulate expression of genes, ensuring that they are active only in appropriate segments
-homeobox is sequence of DNa made up of 180 base pairs within homeotic genes
-functions to produce part of a protein that attaches to DNA of other genes, activating or blocking their expression
-Hox genes- genes of the homeobox that found universally throughout animals
-significant b/c can now compare Hox genes of different organisms and find whether the location of particular organ differs across many species. When two species have similar Hox genes, we can say they are close related evolutionarily