1521 Midterm 2 Growth and Reproduction
The diagram below depicts plant plasmodesmata. What are its functions?
a route for signalling molecules to pass allow for water and sugar to flow between cells plasmodesmata are segments of of smooth ER and cytoplasm that join two different cells through tiny membrane-lined gaps in the cell wall. they permit exchange of signalling molecules, water, and sugars between adjacent cells. genetic material (DNA) is contained in the nucleus (as well as the mitrochondria and chloroplasts), and is not exchanged between cells. there is recent evidence that mRNAs may be exchanged between cell in certain circumstances, but DNA itself is not. arbuscular mycorrhizal fungi penetrate the plant cell wall and make direct contact with the plasma membrane; however, they do not actually enter the cell itself (penetrate the plasma membrane)
Monogamy is more likely to occur in
a species that lives in a habitat with very scattered resources. monogamy typically occurs when a) care by both parents is required for survival of the offspring and b) males do not have opportunity to mate with multiple females. these situations occur when resources are highly scattered, such that females are not located in the same place (which would enable a male to mate with multiple females) and both parents must take turns acquiring food to feed the offspring.
Spermatogenesis yields 4 mature haploid sperm from one diploid primary spermatocyte. How many mature eggs arise from one primary oocyte?
1 the meiotid divisions in egg production have unequal cytokinesis where the majority of the cytoplasm is included in a single egg. this allows maximal resources to be placed in a single egg. the other 3 cells are discarded.
You hammer a nail into a tree trunk 10 ft above the ground (and the tree is currently 20 ft tall). The tree grows taller at a rate of 2 feet per year. How far above ground level will the nail be in 10 years?
10 primary (vertical) growth occurs at apical meristems. meristems are present at the tips of growing shoots, as well as axillary buds which occur where leaves meet the stem. thus new tissue is added at the tip of the shoot or tip of the roots, not at the base of the stem or roots. (grasses, which have basal meristms, are a major exception to this phenomenon. basal merstems are adaptive in plants which are eaten by grazers, as otherwise their meristematic tissue would be removed by herbivory.)
All of the following are correctly matched "tissue system - function" except: Ground tissue: anchors plant Dermal tissue: protects plant Vascular tissue: moves molecules through plant
A dermal: protection/minimize evaporation above ground vascular: transport/support ground: storage/support/photosynthesis
Which of the following is/are correct for the tissue in the previous question which was not correctly matched to function? nutrient storage water/nutrient transport photosynthesis structural support water acquisition protection
A, C, and D ground tissue in leaves carries out photosynthesis (parenchyma); ground tissue in roots and sometimes other locations carries out storage (also parenchyma); ground tissue in the stem also functions in support (collenchyma and sclerenchyma)
The zone of cellular elongation is key for root growth, specifically relying on ____ to achieve cell elongation.
Absorption of water addition of root tissues involves three steps: cell division, cell elongation, and cell differentiation. the root cap is required for protection of dividing cells in the root apical meristem; otherwise these cells would be damaged as they pushed though the soil. once cells have divided, the absorption of water is what causes cells to expand in size. after they expand, they differentiate and root hairs develop.
Which of the following is a function of the plant stem? Allows plants to compete for access to light Provides structure and support to the leaves Transports water to the roots and sugars to the leaves Provides defense against herbivory and pathogens
Allows plants to compete for access to light Provides structure and support to the leaves Provides defense against herbivory and pathogens by growing taller, the stem helps the plant compete with other plants for access to light; the vascular tissue and the collenchyma and sclerenchyma aid in structural support; the dermal covering is covered in a waxy cuticle and can include spines and trichomes which aid in defense against herbivores and pathogens. the transport of sugars occurs from leaves to roots, and transport of water occurs from roots to leaves.
Match each structure with its function in sexual reproduction of angiosperms
Anther - Location of micropsorocyte meiosis and pollen grain development Carpel - Location of both the female gametophyte and all related structures Filament - Stalk linking anther to flower Ovary - Location of megasporocyte meiosis and ovule development Petal - Attract pollinators Sepal - Protect developing flower bud Stamen - Location of both the male gametophyte and all related structures Stigma - Receive pollen Style - Stalk linking stigma to ovary Pollen grain - Male gametophyte Embryo sac - Female gametophyte
Cytoplasmic determinants:
Are located in specific regions within the unfertilized egg Are usually mRNAs or proteins Are distributed unequally in different blastomeres as a result of cleavage cytoplasmic determinants have two defining features: they are asymmetrically located throughout the egg (for example, in a concentration gradient across the egg), and they are deposited from the MATERNAL genome. they are not derived from the embryonic genome. cytoplasmic determinants are typically mRNAs or proteins derived from the maternal genome. tissue-specific proteins are transcribed later on during embryonic development, from the embryonic genome, as part of cell differentiation (becoming specialized cell types). if cytoplasmic determinants where distributed equally throughout the egg, then they would not provide different instructions to different blastomeres (cells resulting from cleavage) during early development. in fact there are many maternally-deposited molecules which ARE distributed evenly throughout the egg, but these molecules do not function as cytoplasmic determinants specifically because they are present equally in all blastomeres.
Which of the following ensures species-specific fertilization?
Bindin proteins in sperm membrane
Which of these structures is NOT formed during gastrulation? Blastocoel Archenteron Endoderm Mesoderm Ectoderm
Blastocoel Gastrulation is the reorganization of the embryonic cells (blastomeres) of the blastula to create the three embryonic germlayers (endoderm, mesoderm, ectoderm). the archenteron (primitive gut) forms as a result of the movement of blastomeres into the blastocoel. the blastocoel exists prior to gastrulation as a result of cleavage, and is necessary for gastrulation to occur; without the blastocoel, there is no space for the archenteron to form.
Which cell developmental process/es is/are most likely to change the shape of the embryo without affecting size? Cell proliferation Programmed cell death Cell movement or differential expansion Cell differentiation
Cell movement or differential expansion Cell differentiation proliferation (cell division) or cell death will change the number of cells in the organism and are thus more likely to change the size of the organism. differential expansion (in plants) or cell movement (in animals) adjusts the distribution or organization of cells in the organism and are thus likely to change its shape. cell differentiation often results in changes in cell shape; on a large enough scale, this phenomenon can also change the overall shape of the organism without affecting size.
Which of the following is/are likley explanation(s) for the diversity in root structures of prairie plants seen below?
Competition Access to water & nutrients this question asks you to consider the function of roots, and how different structures help accomplish that function. the major function of roots is acquisition of water and nutrients. in the presence of competition, roots that grow deeper or wider would have greater access the water and nutrients. access to CO2 is important above ground for photosynthesis; this is mediated by opening and closing stomata on leaves. herbivory results in protective structures like spines on leaves and stems.
If you were to view a sample of animal tissue under a light microscope and notice an extensive extracellular matrix surrounding the cells, which tissue type would you most suspect?
Connective this is part of the definition of connective tissue: connective tissue by definition consists of cells arranged in either a liquid (like blood), jelly-like (like fat tissue), or solid extracelluar matrix (like tendons, bone, or cartilage). Epithelial tissues consist of tightly-packed, sheet-like layers of cells that line organs or the body surface. Nervous tissue consistes of nerve cells and their supporting cells. Muscle tissue consists of bundles of long, thin, contractile cells.
Which of the following observations supports the "good genes" hypothesis to explain male/male competition and female choice? The color and quality of male sage grouse air sacs, used in courtship displays, are extremely sensitive to parasitic infections Ring-tailed lemurs mate only during the autumn breeding season Human males with symmetrical faces are considered more attractive than those with asymmetrical faces Female widow birds prefer males with the longest tails, but males with longer tails are more susceptible to predation
Female widowbirds prefer males with the longest tails, but males with longer tails are more susceptible to predation
Two flowers are both brightly colored and only open during the day, but flower A is highly scented and flower B is not.
Flower A is most likely pollinated by an insect; flower B by a bird •Birds: active during day, respond to visual stimuli •Bees/butterflies/wasps: active during day, respond to visual and olfactory stimuli •Moths: active during night, respond to visual and olfactory stimuli •Bats: active during night, respond to visual and olfactory stimuli
Cells of mammalian embryos remain totipotent (can turn into any cell in the adult body) until the 16-cell stage. This suggests that mammalian embryos:
Do not have cytoplasmic determinants the fact that any mammalian blastomere up to the 16-cell stage can become a normal embryo indicates that the blastomeres do not have 'restricted cell fate.' this means they do not have specific changes in their gene expression to make them different from any other blastomere. this scenario would be impossible if mammalian cells had cytoplasmic determinants, because cytoplasmic determinants (by definition) are asymmetrically located throughout the egg genome and control blastomere fate by altering transcription in the blastomeres that contain them. in the absence of cytoplasmic determinants, all blastomeres would transcribe the same sets of genes as each other. in fact there are many maternally-deposited molecules which ARE distributed evenly throughout the egg, but these molecules do not function as cytoplasmic determinants specifically because they are present equally in all blastomeres. mammalian eggs actually have very small amounts of yolk, which is evenly distributed (consistent with the phenomenon discussed here). speed of development or cell division is irrelevant here: if there are cytoplasmic determinants, then it doesn't matter how quickly or how slowly the cells in an egg divides; ultimately they will end up with different genes expressed if there are cytoplasmic determinants present in the egg. finally, cell-cell signaling is central to development in ALL organisms, and take over the processes of development after cytoplasmic determinants cease playing a role in later development. in the absence of cytoplasmic determinants at all (as in the case of mammalian eggs), then cell-cell communication plays an even more important role in initiating differences between cells during development.
As cleavage progresses, cells in the embryo:
Get smaller during cleavage, the embryo stays the same size. in order for this to occur, the cells in the embryo divide without growing between cell divisions, and thus they get smaller with every division. differentiation, the process of becoming a specialized cell time, occurs much later in embryonic development.
All of the following are correctly matched "tissue system - function" except: Ground tissue: anchors and provides support Dermal tissue: protects plant Vascular tissue: moves molecules and provides support Answer
Ground tissue: anchors and provides support dermal: protection/minimize evaporation above ground vascular: transport/support ground: storage/support/photosynthesis
If an embryo stays the same size during cleavage, its cells must skip which stage(s) of the cell cycle?
Growth (G1 and G2) during cleavage, the embryo stays the same size. in order for this to occur, the cells in the embryo divide without growing between cell divisions, and thus they get smaller with every division. they must undergo synthesis phase because this is when DNA is duplicated; in the absence of DNA duplication, two daughter cells could not be produced because there would only be one copy of the genome. they must undergo mitosis, because this is the portion where the duplicated DNA is divided between the two daughter cells. they must undergo cytokinesis, because this is where the cytoplasms and plasma membranes of the two daughter cells are separated to create two independent cells.
Which of these choices represents a major difference between the reproductive cycles of plants and humans? Humans produce gametes (sperm and eggs); plants produce spores. The reproductive cycle of humans involves haploid and diploid phases; that of plants involves only haploid phases. Human gametes are formed by meiosis, and plant gametes are formed by mitosis. Meiosis occurs in humans but not in plants. Human spores develop into sperm or eggs, and plant spores develop into seeds.
Human gametes are formed by meiosis, and plant gametes are formed by mitosis. the gametes produced by plants are called eggs and sperm, just as in animals. the reproductive cycle of all sexually-reproducing organisms involves a haploid and diploid cycle; in humans, the haploid portion is only the gametes, while in plants, the haploid cycle includes the spores, the gametophte, and the gametes. meiosis produces sperm and eggs in humans, and spores in plants. in eukaryotes, a spore is a haploid cell that is capable of developing into a multicellular, adult organism; humans do not make spores.
Which of the following factors could be a plausible ultimate (evolutionary) driver of hypodermic injection as a mating strategy?
It allows males to place sperm nearer the eggs It allows males to bypass barriers like mating plugs in the female genital tract.
What is the significance of the archenteron?
It will become the digestive tract the archenteron results from invagination of cell into the blastocoel during gastrulation. it is the privitive gut which will become the digestive tract, and is the beginning of the 'tube within a tube' organization of most animal body plans. the archenteron is lined with endoderm (inner tissue layer), while the mesoderm is between the endoderm and the ectoderm (outer tissue layer). gastrulation initiates at the blastopore, which is the site where endodermal cells begin transit into the blastocoel.
Which of the following statements about the deep sea is/are true? It's big Food is abundant Finding a prospective mate can be challenging Identifying a prospective mate is easy Many of its inhabitants are predators
It's big Finding a prospective mate can be challenging Many of its inhabitants are predators
As an animal gets larger, which of the following occurs? Its surface area grows more rapidly than its volume. Its volume grows more rapidly than its surface area. Its volume and surface area increase in proportion to each other. Its volume increases, but its total surface area decreases.
Its volume grows more rapidly than its surface area.
Match the strategy to the male which benefits from that strategy.
Large ejaculatory volume-Second (or final) male advantage Mate guarding - First male advantage Copulatory plugs- First male advantage Elaborate penis morphology - Second (or final) male
Most leaves are adapted to maximize surface area to volume ratio for maxiumal sunlight exposure. In contrast, needle-like leaves have a minimized surface area to volume ratio. The adaptive function of needle-like leaves is to:
Minimize water loss plants with needle-like leaves live in arid environments and face a trade off between photosynthesis and dehydration. narrow leaves minimize surface area to minimize water loss. this results in decreased gas exchange and photosynthesis, but this trade off is worth it because dehydration would result in death.
Why do most hermaphrodites avoid self-fertilization? Briefly describe the factor(s) that select against self-fertilization.
No increase in genetic diversity; Lack of genetic variation
Which structure produces signaling molecules that induce neural tube formation?
Notochord cells of the notochord secrete signals which induce folding of the dorsal ectoderm to form the neural tube. the notochord is mesodermal in origin, but it is specifically the notochord and not mesodermal cells in general that induce formation of the notochord. somites form along side the neural tube after it is formed. the coelum, or body cavity, does not contain cells and does not secrete signals during development.
Which structure develops into fruits? Seeds Ovaries Ovules Flowers Stems Endospores Carpels
Ovaries the ovary, which contains the ovules, which contain the embryo sac (female gametophyte), develops into a fruit if double fertilization and early embryonic development into a mature seed is successful. ovaries are located at the base of the carpel.
What is the relationship between ovule, ovary, and seed?
Ovaries contain ovules; ovules become seeds after they are fertilzed
Palisade mesophyll cells are the site of most photosynthesis in the leaf. These cells are a type of:
Parenchyma cell parenchymal cells have thin, flexible cell walls and can be useded for storage, photosynthesis, and also differentiate into vascular cells (parenchyma rays). collenchmya cells have thicker primary cell walls and retain the ability to stretch and elongage over time; they are used for structural support in growing stems and stalks. schlerenchyma have secondary cell walls of lignin (significant component of wood), and support mature stems after growth has ceased; they can differentiate into xylem cells, and are dead at functional maturity. vessel elements (and tracheids) are part of xylem vascular tissue; they have secondary cell walls of lignin and are dead at functional maturity; pits between adjacent cells permit movement of water. sieve cells and companion cells are phloem cells; sieve cells are chains of cells devoid of organelles to promote movement of sugars through the cell cytoplasm; companion cells are specialized parenchyma cells with organelles that support the organelle-less sieve tube cells. epidermal cells comprise the dermal layer of the plant, and secrete a waxy cuticle (on leaves and stems, but not roots); they include stomata which open and close to regulate gas exchange and minimize water loss, and trichomes which are specialized hair-like structures with a variety of functions.
Which of the following is gametophyte tissue? Stigma Pollen tube Sepal Fruit Integument
Pollen tube the male gametophyte is pollen (contains the tube cell and the generative cell), the female gametophyte is the embry sac (contains the egg, polar nuclei, synergids, and antipodal cells). the pollen tube grows from the tube cell in the pollen through the style of the flower to reach the ovule, which contains the female gametophyte. thus the pollen tube is gametophyte tissue. flowers are sporophyte tissue. the stigma is the part of the flower that the pollen grain adheres to; the sepals are leaf-like structures that contain and protect the flower bud while it is developing; the integument is the sporophyte tissue within the ovule immediately surrounding the female gametophte. the fruit developes from the ovary. ovaries contain ovules which contain the female gametophte. thus fruits are also sporophyte tissue.
Fertilization in all animal species results in formation of a fertilization envelope which:
Prevents more sperm from fertilizing the same egg polyspermy is prevented first by the short-lived fast block (egg membrane depolarization) and the long-lived slow block caused by separation of the vitelline envelope from the egg plasma membrane; once the vitelline envelope lifts away from the plasma membrane, it is called the fetilization envelope. the zygote is protected from dehydration by the amnion of the amniotic egg (in amniotes) or by being laid in water in non-amniotes. implantation in the uterine wall only occurs in placental mammals, and is mediated by the extra-embryonic tissues of the blastocyst.
What is the role of the Ca2+ signal in the egg?
Release proteases to digest bindin receptors on egg sperm-egg membrane fusion causes a Ca2+ wave under the egg plasma membrane. this reaction initiates fusion of cortical granules, which lie just under the egg membrane, with the egg plasma membrane. these cortical granules release the digestive enzymes into the space between the egg plasma membrane and the vitilline layer, where they digest the sperm bindin receptors that allow the sperm to bind the egg. once these receptors are degraded, the vitelline envelope separates from the egg plasma membrane, causing the the slow block to polyspermy by making it impossible for additional sperm to reach the egg plasma membrane. species-specific fertilization is mediated by the sperm bindin and receptor molecules on the egg that recognize the sperm bindin molecules. (each species has different versions of bindin and bindin receptors.)
Which of the following is/are true of sexual reproduction? Sexual reproduction involves recombination of genetic material. Sexual reproduction produces twice as many offspring as asexual reproduction. Sexual reproduction is advantageous in unfavorable environments. Sexual reproduction is advantageous in the presence of parasites. Sexual reproduction is advantageous in static environments
Sexual reproduction involves recombination of genetic material. Sexual reproduction is advantageous in unfavorable environments. Sexual reproduction is advantageous in the presence of parasites.
What is the significance of the first, asymmetric cell divising in plant embryonic development?
The apical cell becomes the embryo The asymmetric cell division establishes the apical/basal (top/bottom) axis of the plan the initial cell division separates into a small apical cell and a large basal cell. the apical cell goes on to develop into the embryo, while the large basal cell gives rise to the suspensor. this first cell division establishes to top/bottom axis of the plant. as the apical cell continues to divide, the cells closest to the suspensor become root tissue, while the cells further from the suspensor become shoot tissue. the radial axis of the plant is established during later cell divisions from cells that derived from the apical cell.
What is the advantage of a seed requiring a cue to break dormancy?
The cue indicates the environmental conditions are likely to support seedling growth. dormancy can be broken by different signals in different species. these can include water (start of rainy season), specific wavelenghts of light (availability of sun), and fire (fire will have killed old, large competitors for light)
If the chorion were removed from an amniotic egg, what would happen to the embryo inside?
The embryo would have difficulty respiring. Amnion - fluid filled cavity that provides aqueous environment and cushions against mechanical shock; Yolk sac - nutrients - blood vessels transport nutrients from yolk to embryo; Chorion - gas exchange between embryo and air; Allantois - waste disposal sac, also functions with chorion in gas exchange
Which of the following supports development/maintenance of a polygynous system?
The females(s) aggregate for communal offspring care, and the male(s) exploit these groupings for reproductive pursuits. polygynous mating systems require the capacity for a single male to 'monopolize' a group of females; this means that a) the females must all be in one location and b) they cannot all be sexually receptive at the same time. if they are not all located in the same place (ie, resources are scattered, multiple mini-territories), then other males can mate with some of the females when the primary male is not near them. if the females are all sexually receptive at the same time, then other males can mate with females while the primary male is mating with another. in species with low breeding success, multiple males often mate with a single female. in species that aggregate in groups including both males and females, a single male cannot monopolize all females due to the presence of other males.
Sporocytes divide by meiosis to create spores. What is different between the microsporocyte and megasporocyte in angiosperms?
The number of surviving spores. meiosis always involve two cellular divisions to go from 2n to 1n, and it always produces cells with half the ploidy of the original parent cell. the defining feature of alternation of generations is that there is both a multicelluar diploid stage AND a multicellular haploid stage; plant spores always develop into multicellular gametophtes (pollen and the embryo sac, in the case of angiosperms). in the case of the microsporocyte, four surviving pollen grains are produced (four gametophytes.) in the case of the megasporocyte, only one spore survives to become the embryo sac.
A tree will most likely die if the bark is stripped off around the entire circumference of the tree. Which of the following is the primary (most immediate) reason why?
The tree would no longer be able to transport sugars from sites of photosynthesis or storage to the rest of the tree bark is composed of phloem and cork. wood is composed of xylem and pith (ground tissue). removing the bark would remove the phloem, and thus prevent the tree from being able to transport sugars from leaves to the rest of the tree; all structures below the cut site would starve to death. apical meristems would not be impacted; the cork cambium and possibly the vascular cambium would be lost in the specific region that was removed and this would prevent additional growth in this area, but this would not be an immediate cause of death. the tree would likely be susceptible to infection, but this would not be immediate cause of death.
What is the function of the typical root and leaf structural shape?
To increase surface area : volume ratio the purpose of a leaf is to collect light for photosynthesis. by maximizing the surface area to volume, the leaf structure places all photosynthetic choloplasts in close proximity to the surface of the leaf where they are maximally exposed to light.
An ovary contains 20 ovules. How many pollen grains are required in order for all 20 ovules to develop into viable seeds with embryos and endosperm (one sperm is required for each embryo and endosperm to form)?
Twenty, since each pollen tube releases two sperm. double fertilization refers to an angiosperm-specific phenomenon where two sperm are required to create the seed: one sperm fertilizes the haploid egg to create the diploid zygote (embryo) itself, while the other sperm fertilizes the two polar nuclei to produce the triploid endosperm. The endosperm grows into nutritive tissue which is then metabolized by the growing embryo. the pollen tube grows from the tube cell in the pollen grain (the male gametophyte) through the style of the flower to reach the ovule, which contains the female gametophyte. the generative cell in the pollen grain produces two sperm; thus one pollen grain produces the two sperm required to accomplish double fertilization.
A woody plant increases in width due primarily to cell division in:
Vascular cambium, which makes new vascular tissue (xylem and phloem) apical meristems add vertical growth (length). cork cambium creates part of the bark; bark is a relatively thin layer of tough dermal tissue containing cork and phloem, and does not contribute to expanding width. expanding width is achieved primarily by addition of xylem cells from the vascular cambium; vascular cambium also produced phloem, which is part of the bark.
If an egg distributed all the constituents of its cytoplasm uniformly, which of the following outcomes is most likely?
all daughter cells will express the same set of genes cytoplasmic determinants are asymmetrically located throughout the egg genome. cytoplasmic determinants are transcriptional regulators and thus control blastomere fate by altering transcription in the blastomeres that contain them. if cytoplasmic determinants where distributed equally throughout the egg, then they would not provide different instructions to different blastomeres during early development, and thus all blastomeres would transcribe the same sets of genes as each other. in fact there are many maternally-deposited molecules which ARE distributed evenly throughout the egg, but these molecules do not function as cytoplasmic determinants specifically because they are present equally in all blastomeres.
In mammals, identical twins are produced by the separation of cells during
blastomere cleavage in order for a cell to be capable of forming a new organism, it must not yet be 'specified' for a specific cell fate (ie, becoming a skin cell, or an anterior part of the body, or ectoderm, etc). at gastrulation (and of course later on in development), cell-fate differences have already been established. thus identical twins can only form from cells prior to gastrulation, during cleavage. this phenomenon is true of organisms that do not use cytoplasmic determinants in the egg to specify cell fate. if cytoplasmic determinants are present, and the very first cell division causes unequal partitioning of the cytoplasmic determinants, then cells can already have cell-fate-specific information during the first blastomere cleavage.
Which of the following plays a role in cells "knowing" where they are in an embryo and thus what type of cells they should become (differentiate into) during development? cell proliferation programmed cell death cell movement or differential expansion cell-cell signaling/induction cytoplasmic determinants
cell-cell signaling/induction cytoplasmic determinants cytoplasmic determinants set up initial identity/location information in many lineages including protostomes and some vertebrates. cytoplasmic determinants are important early in development during cleavage, but they are quickly 'titrated out' in later development, when cell-cell signaling (induction) becomes much more important in establishing identity/location information. the other developmental processes (movement, proliferation, programmed cell death) are all regulated by cell-cell signaling
In humans, spermatogenesis and oogenesis differ in that:
cytokinesis is unequal in oogenesis, whereas it is equal in spermatogenesis
Which of the following directors of embryonic development can be found within unfertilized eggs of protostomes? mRNAs transcribed from embryonic genome bindin proteins tissue-specific proteins cytoplasmic determinants
cytoplasmic determinants cytoplasmic determinants have two features: they are asymmetrically located throughout the egg (for example, in a concentration gradient across the egg), and they are deposited from the MATERNAL genome. they are not derived from the embryonic genome. cytoplasmic determinants are typically mRNAs or proteins derived from the maternal genome. tissue-specific proteins are transcribed later on during embryonic development, from the embryonic genome, as part of cell differentiation (becoming specialized cell types). bindin proteins are present on mature sperm and are used to mediate sperm-egg binding during fertilization.
During fertilization, the acrosome
digests the coatings surrounding the plasma membrane of the egg the acrosome is a compartment in the sperm that contains digestive enzymes. contact between the sperm and the jelly layer/zona pellucida initiate release of the digestive enzymes which degrade the jelly layer. polyspermy is prevented by the short-lived fast block (egg membrane depolarization) and the long-lived slow block caused by separation of the vitelline envelope from the egg plasma membrane. sperm mitochondria are nourished by component of the semen such as citric acid and sugars. the sperm nucleus enters the egg upon membrane fusion between egg and sperm.
The nervous system originates from
ectoderm the nervous system originates from ectodermal tissue which folds in on itself to create the neural tube (which will become the brain and the nerves of the vertebral column in vertebrates). the creation of the neural tube is due to signals from the underlying notochord.
One advantage of asexual reproduction is that it:
enables individuals in the species to rapidly colonize habitats that are favorable to that species the origin of genetic diversity in asexual reproduction is mutation (and in the case of bacteria, horizontal gene transfer). in contrast, sexual reproduction includes both mutation and recombination of alleles during gametogenesis and gamete fusion as sources of genetic variation. dormancy is a phenomenon related to surviving unfavorable conditions, which can occur in both sexually and asexually reproducing organisms. sexual reproduction is typically more advantageous in rapidly changing environmental conditions due to increased opportunities for genetic recombination. harmful mutations are more easily eliminated from the population in asexual reproduction in that the individuals with these mutations are less likely to pass on their alleles and the harmful mutations cannot be recombined into other genomes through sexual recombination; however, this occurs at the population level and is not an advantage to the individual. because asexual reproduction is faster than sexual reproduction, asexual reproduction offers a huge advantage to organisms colonizing a new environment if they are well adapted to it. sexual reproduction offers a better advantage in the presence of pathogens and parasites, due to increased opportunities for genetic recombination.
Sperm cells mature and are stored within human males in the _
epididymis mature sperm are stored in the epididymis. the urethra is the shared urogenital tube that transports urine and semen outside the body. the bulbourethral glands produce alkaline mucus added to semen immediately prior to ejaculation. the seminal vesicles produce fructose and prostaglandins aded to semen immediately prior to ejaculation. the prostate gland produces antibiotics and citric acid to semen immediately prior to ejaculation.
what is the difference between eudicot and monocot roots and stems
eudicot root, based on star-shaped stele in center; II - monocot stem, based on randomly distributed vascular bundles; III - eudicot stem, based on well organized ring of vascular bundles around periphery; IV - eudicot stem demonstrating secondary growth, based on rings of secondary xylem
If a dehydrated seed must re-imbibe water in order to germinate, what is the advantage of drying out to begin with?
lighter in weight to facilitate dispersal ensures germination only occurs when conditions are good protects seed from freezing to death the biological purpose of a seed is dispersal; the seed provides protection and food stores to help the new organism successfully germinate and grow in a new location from the parent organism. loss of water makes the seed weigh less, and protects the seed from freezing as expanding ice crystals are very destructive to biological tissues. the presence of water after drying out is a useful signal to germinate, since it can indicate the start of a rainy season when growth conditions will be good.
Gametes are produced by [blank] in the haplontic life cycle, by [blank] in the diplontic life cycle, and by [blank] in the alternation of generations life cycle.
mitosis; meiosis; mitosis gametes are always haploid, regardless of the ploidy of the organism that produces them. if the organism is haplid (haplontic life cycle), then the only cellular process to make haploid cells is mitosis, because mitosis creates cells which are identical to the parent cell. if the organism is diploid (diplontic life cycle), then the only cellular process to make haploid cells is meiosis, because meiosis reduces ploidy by half. in alternation of generations, the diploid organism produces haploid spores (via meiosis) which grow into haploid multicellular organisms. these haploid multicellular organisms produce gametes via mitosis.
Embryonic cells can learn their position by "reading" the concentration of a
morphogen this is the definition of a morphogen, a molecule that exists in a concentration gradient and provides spatial information to the embryonic cells based on the local concentration. some morphogens are hormones, such as auzin in plant development; some morphogens are mRNAs or proteins, such as biocoid in fruit fly development. Hox genes are far down the cascade of events that play a role in development, and are ultimately activated much later in development as a result of genes which were activated by genes which were activated by genes which were activated by (etc.) the original morphogen. Hox genes also are not present in concentration gradients.
Paralogs are homologous genes that arise by gene duplication, meaning that an organism has an additional copy of the gene in question. If a mutation alters the protein-coding region of one of the paralogs, then:
natural selection can act independently on each gene copy, often leading to the evolution of two distinct genes. any time a gene duplicates, the organism now has two genes that encode the same protein and thus have the same function. if mutations occur in one gene and alter its function, the other copy of the gene can still carry out the original function. paralogs are one important way that new traits arise in species, for example maternal vs fetal hemoglobin proteins. hox gene duplications (paralogs) are closely correlated with speciation events in animals, suggesting new segment identities play an imporant role in animal speciation.
Physical removal of which of the following structures from a vertebrate embryo would likely cause defects in limb muscle formation?
notochord neural tube dorsal ectoderm somites he most immediate structure required for limb muscle development is the somites; cells in the somite migrate to the limbs to develop into muscles, so removal of somites would prevent development of muscles. the somites arise and become specified for certain celll fates due to a combination of signals from the notochord, the dorsal ectoderm, and the neural tube. cells of the notochord secrete signals which induce folding of the dorsal ectoderm to form the neural tube. somites then form along side the neural tube after it is formed. thus removal of any of these structures could prevent development of limb muscles. in contrast, ventral endoderm is not involved in any of these processes.
Which of the following conditions favors evolution of a polyandrous mating system? offspring require a high degree of paternal care for survival females live together in large social groups males provide no parental care males compete for access to females
offspring require a high degree of paternal care for survival polyandry is rare and the ecological factors that favor it typically involve very low survival rates of offspring such that females must constantly reproduce in order for any offspring to survive. this means females are not available to raise the young, as they would be unable to produce additional young if they had to care for an existing brood or clutch. therefore in polyandry there is typically a "role reversal" between males and females in terms of rearing young. females abandon the nest (jacana birds) or transfer eggs to the male's brood pouch (pipefish). thus the offspring only survive (and the male ensures reproductive success) only if he cares for them. in polyandry, females compete for access to males.
Fertilization of a human egg takes place in the
oviduct sperm can survive in the oviduct for ~3-4 days. fertilization must in the oviduct immediately after ovulation. the cleavage divisions occur in the oviduct as the fertilized egg moves toward the uterus.
Select all of the following which comprise the wood of a woody stem in a mature tree: pith primary xylem secondary xylem primary phloem secondary phloem cork
pith primary xylem secondary xylem bark is composed of phloem and cork. wood is composed of xylem and pith (ground tissue). thus the vascular cambium, which produces both new xylem and new phloem, is the boundary between wood and bark.
Why is this statement wrong? "Hox genes control the locations of specific parts of the body plan of plants and animals, such as the locations of eyes, limbs, or leaves."
plants don't have Hox genes
The major function of meristematic tissue is to:
produce more cells meristematic tissue is analogous to stem cell tissue in animals; it is constantly producing new cells to facilitate new growth. apical meristems produce up or town growth (stems and roots); lateral meristems add width
Select all of the following which comprise the bark of a woody stem in a mature tree: pith primary xylem secondary xylem primary phloem secondary phloem cork
secondary phloem cork bark is composed of phloem and cork. wood is composed of xylem and pith (ground tissue). thus the vascular cambium, which produces both new xylem and new phloem, is the boundary between wood and bark. primary phloem (the phloem present in the first year of growth) is not present in mature trees because it becomes crushed into/by the cork cambium
Among non-mammalian vertebrates, the cloaca is an anatomical structure that functions as
shared pathway for the digestive, excretory, and reproductive systems this is the definition of the term cloaca. cloacas are present in vertebrate lineages such as amphibians, reptiles, birds, cartilaginous fish, and monotremes. they are not present in placental mammals and most bony fish.
What are the "costs" associated with sexual reproduction?
slow, higher energy cost, requires finding a mate, disrupts good allele combinations
What are the "costs" associated with sexual reproduction?
slow, higher energy cost, requires finding a mate, may disrupt good allele combinations
which cells will become the plant's roots.
the circled structure at the bottom is the root apical meristem, which will give rise the root tissue upon germination. the circled structure at the top is the shoot apical meristem, and will give rise to the shoot system (stem and leaves) upon germination. the cotyledons, or embryonic leaves, are on either side of the shoot apical meristem. the structure at the bottom of the diagram is the basal cell and suspensor, which anchor the embryo within the seed during development.
Cell differentiation always involves
the production of tissue-specific proteins, such as muscle actin
Females of many insect species, including honeybee queens, can store gametes shed by their mating partners in
the spermatheca his is the definition of the term spermatheca. spermathecas are present in many invertebrate species such as insects, worms, and some molluscs. females in some species have multiple spermathecas which can store sperm from a single or multiple males, allowing fertilization of eggs for months after a single mating. sperm from the spermatheca fertilizes the egg as it passes through the oviduct.
Double fertilization is a component of the angiosperm life cycle, and produces:
the zygote and endosperm double fertilization refers to an angiosperm-specific phenomenon where two sperm are required to create the seed: one sperm fertilizes the haploid egg to create the diploid zygote (embryo) itself, while the other sperm fertilizes the two polar nuclei to produce the triploid endosperm. The endosperm grows into nutritive tissue which is then metabolized by the growing embryo. the pollen tube is part of the male gametophyte (pollen); it grows from the pollen grain on the flower stigma through the flower style to reach the ovary. the two sperm travel through the pollen tube to reach then female gametophyte (embryo sac which contains the egg and polar nuclei) inside the ovule. the ovule is the structure inside the ovary which contains the female gametophyte (embryo sac).
There are population of snails in New Zealand that can produce sexually or asexually. The snails are parasitized by a type of worm. Given what you know about conditions that favor sexual or asexual reproduction, you would expect to see the snails produce asexually when:
there are few parasitic worms in the environment because asexual reproduction is faster than sexual reproduction, asexually reproducing organisms have a huge advantage of sexually reproducing organisms when conditions are favorable; if the asexual organisms are well-adapted to the environment, they will quickly out-compete sexually reproducing organisms. sexual reproduction offers a better advantage in rapidly changing environments, unfavorable conditions, or in the presence of pathogens and parasites, due to increased opportunities for genetic recombination. the presence of parasitic worms would favor sexual reproduction because the worms would rapidly adapt to the asexually reproducing snails who only have mutation as a means of genetic diversity; sexually reproducing snails have mutation and genetic recombination as sources of genetic diversity.
Which of the following best describes the ploidy level of the cells found in the embryo sac after fertilization? There are haploid, diploid, and triploid cells. All cells are polyploid. All cells are triploid. All cells are diploid. The ploidy level varies among species.
there are haploid triploid and diploid cells the antipodal cell sand synergid cells are haploid; the embryo is diploid, and the endosperm is triploid.
Which of the following is true of Hox genes? they control the locations of specific parts of the body plan of plants and animals, such as the locations of eyes, limbs, or leaves they are evolutionarily conserved in all animals except sponges they activate expression of genes which control development of body segments they are chemical signals present in the unfertilized egg changes in Hox genes have contributed to rapid diversification of animal lineages
they are evolutionarily conserved in all animals except sponges they activate expression of genes which control development of body segments changes in Hox genes have contributed to rapid diversification of animal lineages Morphogens are present in concentration gradients in the unfertilized egg. Hox genes are far down the cascade of events that play a role in development, and are ultimately activated much later in development as a result of genes which were activated by genes which were activated by genes which were activated by (etc.) the original morphogen. Hox genes also are not present in concentration gradients. Hox genes control segment identity in animals, specifying where eyes, legs, etc. should develop; they are evolutionarily conserved in all animals except sponges (thus a synapomorphy in all animals excelt sponges). Evolution of different animal groups closely (but does not completely) correlated with duplications in Hox genes, suggesting they are an important contributor to speciation events in animal lineages. Hox genes are not present in plants; MADS box genes play an analagous role in plant development, though MADS box genes and Hox genes are not evolutionarily related.
What separates wood from bark?
vascular cambium bark is composed of phloem and cork. wood is composed of xylem and pith (ground tissue). thus the vascular cambium, which produces both new xylem and new phloem, is the boundary between wood and bark.
One important difference between the anatomy of roots and the anatomy of leaves is that _
waxy cuticle covers leaves but is absent from roots the waxy cuticle minimizes evaporation above ground; however, one of the main functions of roots is to absorb water - if roots were covered in a waxy cuticle, they would be unable to absorb water
In species that are capable of both sexual and asexual reproduction, under which of the following conditions is sexual reproduction more likely to occur?
when conditions for survival are unfavorable because asexual reproduction is faster than sexual reproduction, asexually reproducing organisms have a huge advantage of sexually reproducing organisms when conditions are favorable; if the asexual organisms are well-adapted to the environment, they will quickly out-compete sexually reproducing organisms. sexual reproduction offers a better advantage in rapidly changing environments, unfavorable conditions, or in the presence of pathogens and parasites, due to increased opportunities for genetic recombination.
