Biology of Plants
Evolution of female reproductive coverings. In this course we have traced this evolution from isogamete, to anisogamete, to egg, to egg in oogonium, to egg in archegonium as we went from algae through fungi to bryophytes and ferns. It is a pathway of coverage in which the female reproductive structures that once were free-living swimming forms have evolved into forms contained in layers of coverage. Trace the continued evolution through Selaginella, Gymnosperms and Angiosperms. Don't write a book for each, but tell about the main innovation regarding coverage of the female phases in each group of organisms.
wrapped by carpel
This last section of evolution has also shown great changes in the megagametophyte. Describe the megagametophyte of each of these three life histories. You do not need to mention the coverage of the gametophyte, just the gametophyte itself. For a moss, one might write: thallus, rhizoid, "stem", "leaf", archegonium, egg.
thallus, rhizoid, archegonium, egg
thallus, archegonium, egg
antipodals, central cell, synergids, egg
I'm sure you will not be surprised that the next question is to describe the microgametophyte of these three organisms to show the direction of evolution in this important structure. Here please also write some words about numbers and kinds of gamete(s) produced.
endosporic, antheridium, many sperm, motile sperm
spore wall, prothallial cells, tube cell, generative cell, two sperm, +/- motile sperm
spore wall, tube cell, generative cell, two sperm, non-motile sperm
Pollination botany deals with innovations that plants have evolved to achieve pollination. Describe the important features of flowers that make it possible for them to be pollinated by bees or wasps.
|The equivalent of a stamen in a pine cone is||microsporangiate cone scale|
|The equivalent of a carpel in a pine cone is||megasporophyll|
|The equivalent of a petal in a pine cone is||bract|
|The equivalent of a locule in a pine cone is||none|
Diagram a longitudinal section of a flower and label it as completely as you can.
In the following table, compare the structure and organization of primitive and advanced flowers.
|Primitive Flower||Advanced Flower|
|many parts||fewer parts|
|elongate axis||short axis|
|beetle pollinated||bee, wind pollinated|
|superior ovary||inferior ovary|
|large flowers||tiny flowers|
|single flowers||gathered into head|
|all flowers same||division of labor|
Diagram an angiosperm pollen grain (microgametophyte) and an embryo sac (megagametophyte) and label them completely.
|What would you add to the angiosperm pollen grain to make it a pine pollen grain?||1.spore wall sacs|
Describe what is unusual about syngamy in angiosperms?
|it is double|
You have learned about extensive free-nuclear stages in both Pine and Angiosperms.
|What has to happen for a cell to become free-nuclear?||mitosis|
|What is the major free-nuclear stage in Pine?||megagametophyte|
|What is the major free-nuclear stage in Angiosperms?||endosperm|
|What three things constitute a seed?||1.seed coat|
There are three distinct ways to classify a fruit. Tell the main features of each of them.
|1. Origin:||simple - one flower one fruit|
aggregate - one flower many fruits fused together
multiple - many flowers many fruits fused together
|2. Composition:||true - ovary wall only|
accessory - includes receptacle, etc.
|3. Description:||fleshy - juicy wall when mature|
dry - papery or hard wall when mature
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