Question 1: Conifer and Flowering Plant Life Histories, biology homework help

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Question 1: Conifer and Flowering Plant Life Histories

Discuss the life histories of a pine (Coniferophyta) and a flowering plant (Anthophyta). Include in your discussion:

a. the sequence of stages in the life histories of each and their reproductive structures

b. definitions of seeds and fruits including the structures of each

c. factors that may have influenced the distribution and success of these seed-bearing plants (Hint: plant structure and form, mechanisms of water conservation and distribution, pollination and seed dispersal mechanisms, including coevolution of the animal groups often involved in these mechanisms, should be prominent features of your answer)


Question 2: Invertebrate Animal Life Histories

Describe the life histories of animals with indirect and direct development. Include in your answer:

a. a comparison of the life histories of two freshwater invertebrates: the Cool Weather Mosquito (Culiseta incidens) and the Giant Water Bug (Abedus indentatus)

b. a comparison of two marine invertebrates: the Iridescent Phyllodoce (Phyllodoce multipapillata) and the Market Squid (Loligo opalescens

) c. definitions of r-strategies and k-strategies of reproduction and the advantages of each under different conditions

d. a description of the life history ("life cycle") of trematode parasites of the estuary with emphasis on those aspects that increase the probability of their completion despite the complexity of their life histories


Question 3. Sexual Reproduction Define sex. What differentiates asexual reproduction from sexual reproduction? Include in your answer:

a. a description of the various types of asexual and sexual reproduction and under what circumstances each is more beneficial than the other

b. the benefits of sexual reproduction to populations and evolution

c. explanations of the various “costs of sex”


Question 4. Divergences from Stem Reptiles: Dinosaurs, Birds and Mammals Describe the sequence of divergence of dinosaurs, birds and mammals from their nearest reptilian ancestors and their adaptations for “warmbloodedness” (endothermic homeothermy). Include in your answer:

a. a description of reptilian radiation and the origins of dinosaurs, birds and mammal and the timing of these divergences

b. support the contention that birds are not simply derived from dinosaurs, but are dinosaurs

c. definitions of ectothermic poikilothermy and endothermic homeothermy

d. the many physical fossils that provide evidence of the evolution of “warm-bloodedness” in dinosaurs and mammals and the reason that each piece of evidence demonstrates an evolution toward endothermic homeothermy in the two independent groups.


Notes: Although there is a minimum word count 3500 words for this exam, you will find that it is likely going to require more than the minimum to fully answer the question. You may not copy or quote from any source. All information must be re-written in your own words. Answer all question.

You must have a References section with at least five references which you have used in preparing your answers: the course website, the textbook, and at least three additional sources.

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The word document contains all the written essays that address the four assignment questions.


Surname 1
Student’s Name
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Question 1: Conifer and Flowering Plant Life Histories
Coniferophyta: Conifers are cone-bearing plants that carry both female and male
sporophylls on one sporophyte. For this reason, they are monoecious plants (Brodribb et al,
2005). Pines are gymnosperms, hence heterosporous, producing both the female megaspores and
the male microspores (Brodribb et al, 2005). The microsporocytes in male cones produce pollen
grains through meiosis. Pollen is released in large amounts during the spring and is carried by the
wind to the female cone. The growth of the pollen tube is initiated, this is known as pollination,
it takes place slowly as the cell present in the pollen grain undergoes mitosis to form two haploid
sperm cells. One sperm cell unites its nucleus with the nucleus of the egg cell during fertilization
(Brodribb et al, 2005). Female cones are made up of two ovules; the megasporocyte in each
ovule undergoes meiosis. A single cell is left after the breakdown of three cells; this cell forms a
multicellular gametophyte which encloses archegonia. On fertilization, an embryo is formed
from the diploid egg (Brodribb et al, 2005). Three generations of tissues make up the seed
formed; the gametophyte which provides nutrients, the embryo, and the seed coat developed
from the sporophyte tissue. The seed, at maturity, drops on the ground from the cone,
germination occurs whereby the seedling grows into a plant, the mature adult plant also produces
cones. The cycle continues thereafter (Brodribb et al, 2005).

Surname 2
Seeds and ovules of the pine are located on upper surfaces of the female cone, which
grows on the upper branches, thus exposed in the cone scales. This eases the received of pollen
grains from the wind for pollination to take place (Farjon, 2008). The male cones, on the other
hand, grow in lower branches of the pine. The leaves of conifer trees have a needle-like shape
which enables them to survive in harsher and colder conditions easily as compared to trees with
broad leaves. This needle leaf design with tightly packed leaves also protects the central vein of
the leaf that contains the vascular tissue. The reduced surface area of the leaf reduces water loss
through evaporation (Farjon, 2008). The needles are also covered with a waxy cuticle that slows
down water loss through transpiration, the waxy cuticle, together with sclerenchyma, protect the
photosynthetic cells in the leaves (Farjon, 2008). These needles are also an adaptation that
protects these plants against consumption by animals because of their bad taste. Conifers have a
cone shape which together with the needle-like leaves, allow for easy gliding off of snow thus
the branches are not subjected to the accumulation of a lot of weight (Farjon, 2008).
Anthophyta: The main phase of the life cycle of an angiosperm is the sporophyte or adult.
Angiosperms are also heterosporous, they form microspores which produce male gametophytes
in form of pollen grains, and megaspores which form ovules that contain female gametophytes.
Through meiosis, the male gametophytes divide to form haploid microspores in the anthers,
these, in turn, form pollen grains through mitosis. Each pollen grain is made up of one cell that
divides into two sperms and another cell that forms the pollen tube. The ovary shelters ovules
which contain the megasporangium that is protected by the ovary wall and two integument
layers. Each megasporangium contains a megasporocyte that goes through meiosis, hence the
formation of four megaspores, one large and three smalls, the large megaspore survives,
producing the embryo sac, which is the female gametophyte. The megaspore divides thrice

Surname 3
forming an eight-cell stage; two cells migrate to the equator and form a polar nucleus after fusion
and four cells migrate to each pole of the embryo sac. Antipodals are formed by the three cells
that are away from the egg while synergids are formed by the two cells located closest to the egg
(Brodribb et al, 2005). At maturity, the embryo sac contains the three antipodal cells, two polar
nuclei located in a central cell, and one egg cell. Upon reaching the stigma, a pollen grain
extends a pollen tube which grows down the style a...


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Excellent resource! Really helped me get the gist of things.

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