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Describe the major groups that makeup SAR. Name one individual that is characteristic
of each group.
The supergroup SAR is made up of the stramenopiles, the alveolates, and the rhizarians.
The Stramenopiles protists under that group characteristically have two sets of flagella,
one hairy, and one smooth. This group includes a majority of protists that performs
photosynthesis on Earth. A protist under the stramenopile is a diatom. They are tiny
phytoplankton with very rigid glass structures and create diatomaceous earth when
they die. The next group, the Alveolates, characteristically have tiny membrane-sacs
under their plasma membrane similar to the alveoli of the lungs. A very well-known
protist in the alveolates group is the dinoflagellates. They are the main cause of red
tides and releases toxins that kills fish and can harm humans. The last group, the
Rhizarians, are mainly amoebas with threadlike pseudopodia. Forams are protists under
rhizarians that can be used as fossil records.
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Explain the Angiosperm reproductive cycle in detail. Be sure to differentiate between the
sporophyte and gametophyte generations.
An angiosperm life cycle is very long and very complex. The gametophyte stage begins
with the haloid stage. The microsporocytes in the microsporangia on the anther
undergo meiosis first and then mitosis in order to divide. We’re left with haploid pollen
grain that is made up of the tube cell with the generative cell inside of it. On the female
side, in the ovary, the ovule undergoes meiosis to form megaspores. Only one survives
and that contains the integuments, the seed coat, 2 central nuclei, an egg cell, 3
antipodal cells, and 2 synergids. Next begins the sporophyte stage. For fertilization to
occur, a pollen grain lands on the stigma of the flower and the tube cell starts to form a
tube and make its way towards the megaspore by following the synergids signals. Inside
of the tube, the generative cell undergoes mitosis and become the 2 sperm cells. Those
two follows along in the tube cell towards the megaspore. Once the tube reaches the
micropyle in between the integuments, double fertilization starts to occur. The first
sperm cell fertilizes the egg cell and becomes the embryo, and the other fertilizes the 2
central nuclei which will become the endosperm. The whole structure is now the seed.
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What traits do plants have in common with green algae? What derived traits distinguish
plants from green algae? How do these traits facilitate the colonization of land?
Plants and green algae charophyte both are photosynthetic autotrophs, contain
phragmoplast, sporopollenin, and rings of cellulose to synthesize complexes. Plants on
the other hand have spores, embryos, alternation of generation, and apical meristems
which distinguishes them from green algae. With no longer needing water for
fertilization, plants were able to cover more grounds with spores and spread faster.
With apical stems, better chances to get necessary nutrients from the ground.