Plants Lesson 2 Flashcards
Multicellular Haploid in Humans?
It’s like the sperm or egg
Alternation of generation
MULTICELLULAR haploid & diploid stages. All land plants do it. Arose independently in evolution several (or many) times—so also in other groups (like green algae). Arose in the ancestors of all land plants.
What’s the multicellular diploid?
Sporophyte
What’s the multicellular haploid)?
Gametophyte
What are the alternating “generations” ?
Gametophyte (haploid, 1n): makes gametes and Sporophyte (diploid, 2n): makes spores
What makes spores?
Meisois
Steps of plant development?
Spores to gametophyte to gamete
Animal lifecycle
Meiosis makes egg and sperm. They combine to fertilize then make a zygote to adult and back to meiosis.
Land plant lifecycle
(Haploid) Meiosis makes 4 spores. Then they go through mitosis to gametophytes. Then they make egg and sperm. (Diploid) They then combine to fertilize. Then to it go to a sporophyte and back to meiosis.
Spore
Single cell that can divide to produce a multicellular
organism without uniting (often with protective coat).
Gamete
Single cell that can unite with another gamete to
produce a diploid zygote. Can’t divide to produce multicellular organism.
A green alga without alternation of
generations?
Chlorophtya. It spends most of its as a single cell and haploid. It has two flagella. Goes through simple asexual reproduction.
The lifecycle of a green alga without alternation of
generations (asexual reproduction)?
For asexual reproduction a mature cell makes four more of itself (mulitcelluar haploid). It’s in a sac and what it releases a zoospore which is. a mature cell.
The lifecycle of a green alga without alternation of
generations (sexual reproduction)?
Sometimes it will go through sexual reproduction when environmental stresses. The mature cell has + and - signs. The two opposite signs unite and fertilization occurs. Then a zygote is made (2n), which then foes through meiosis and it results on 4 mature cells.
Why doesn’t the green alga have no alternation of generations?
Because there’s no multicellular diploid.
How did alternation of generations originate?
Zygote delays meiosis & divides and grows (multicellular diploid arises). The multicellular haploid parent has the zygote in the archegonium. Then meiosis is delayed and its fertilizes, and instead zygotic mitosis produces multicellular sporophyte. The result is 2 generations. The multicellular haploid (gametophyte) and the multicellular diploid (sporophyte).
How many total divisions of land plants (embrophytes)are there?
10
What 4 divisions of land plants are we looking at in class.
Mosses, ferns, conifers, angiosperms
The mosses
~15,000 species. Low growing (max few cm long). Confined to damp areas because of Swimming sperm.
No true vascular tissue (rudimentary vascular system) (meaning they can’t get fluid around their bodies).
No true leaves (because it only exists with vascular tissue). Gametophyte dominant (larger part of the life cycle). Homosporous (1 spore size).
How do moss sporophytes arise?
From gametophytes. Sporophytes are dependent on it.
Moss life cycle
The spore germinates and turns into a separate male or female gametophyte. There is one egg in each female gametophyte. The sperm are made by mitosis and are then inside the male gametophyte, then the raindrop carries the sperm and lands on the archegonia and the sperm swim down to the egg. Fertilization occurs in the archegonia and immediately creates the new sporophyte. Then it’s a diploid zygote to embryo then young sporophyte. Then sporophyte emerges from the gametophyte, and is mature. Then it makes spores in the sporangium. Then the spores are released through the peristome. All applies to all land plants, the difference is how the structures look.
Germinates
When the spore opens up into a bud.
Male gametophyte in mosses
Antheridia
Female gametophyte in mosses
Archegonia
How does the spore know if it will turn into a female or male gametophyte?
The environment will decide it.
Embryophyte Condition
After fertilizing, when the diploid organisms sits inside and develops in the haploid structure that made the egg.
Rhizoid
The roots of the gametophytes.
Parts of the sporophyte
Seta (stem) and the capsule (sporangium).
Why does the sporophyte stay on the gametophyte?
It’s dependent on it for nutrients because the gametophyte photosythenizes.
Sporangium
A vessel that covers the spores.
Meiosis requires what?
A diploid cell. So haploids can only go through mitosis.
Each sporophyte makes what?
4 spores
Why can vascular tissue make land plants taller?
It supports the plant and provides rigidity, and also supplies the plant with sugar, water, hormones and more.
When did vascular tissue arose?
In the cooksonia about 410 mya.
Properties of ferns (division pterophyta)?
~20,000 species. most tropical. Appeared ~400 mya. Vascular tissue (Xylem & phloem which Support & supply). Swimming sperm (requires water). Sporophyte dominant (it’s the one we see). Homosporous (one spore types) or heterosporous (many spore types).
Lifecycle of a homosporous fern?
Haploid spore turns into a young gametophyte (that’s hermaphroditic) by mitosis. The female and male gametophyte are on the same thing. The sperm then goes into the archegonium and fertilizes. The zygote grows in the gameophyte, then when mature, the sporophyte grows out. Then the gametophyte disintegrates and the mature sporophyte has sporangium on the back of the leaf that then releases spores.
Sorus
On the backside of the fern leaf. It’s a group of sporangium.
Fern sporangium
It;s undr a lot tension. It will break open and throw itself forward and empty the contents. Spores only get a few cm’s away.
What are the cinnamon fern’s two kinds of leaves?
Sexual leaves (makes spores) and vegetative leaves (does photosynthesis).
One of the fastest movements in the living world?
The closing of the fern sporangium.
Homospory
One size of spore from meiosis. Mosses and most ferns have it.
Heterospory
Two sizes of spores from meiosis. Some ferns and all seed plants.
Homosporous spore production
Sporangium on sporophyte to single type of spore to typically a bisexual gametophyte then to either an egg or sperm.
Heterosporous spore production
Megasporangium on megasporophyll to(meiosis) megaspore to(mitosis) female gametophyte to egg. Or microsporangium on microsporphyll to(meiosis) mircospre to(mitosis) male gametophyte to sperm.
The difference in male and female in biology?
The size difference between the female gamete (egg) and male gamete (sperm).
What goes together?
Pollen and seeds
5 divisions (phyla) of seed plants?
Cycadophyta, Gnetophyta, Ginkgophyta, Coniferphyta, Anthophyta
Seeds
Embryo + nutrition + seed coat. Develops from ovule (immature seed) (new evolutionary thing). Novel structure appearing in seed plants. Site of (female) meiosis. Thus contains female gametophyte, female sex organs, egg & embryo. Once the embryo matures you have a seed.
Integument (conifer)
Part of the ovule that’s apart of the parent plants the made the ovule. Will become the seed coat when it matures. The megasproangium (2n nucleus) is inside of it.
Mircopyle (conifer)
Part of the ovule that’s the entrance where the pollen comes in.
What’s in the ovule after meiosis in megasporangium? (conifer)
A single functional megaspore (1n); will become megagametophyte (1n).
The ova;e becomes the seed (conifer)?
Unfertilized ovule to fertilized ovule to gymnosperm seed.
What nourishes the embryo (conifer)?
The female gametophyte.
When does the pollen get to the ovule (conifer)?
Way too early. The pollen sits that the entrance until the female is ready, then it will be let in and meet up with the egg.
In conifers, pollen contains what?
One active sperm.
Pollen
Mature male mircogametophyte. Few cells in size. Contains sperm
Conifers (division confierophyta)
~550 species Reproductive organs in cones. Sporophyte dominant. Heterosporous. Microgametophyte = pollen!. Megagametophyte within ovule, makes egg & then nourishes embryo. All woody- either shrubs or trees.
Conifer life cycle
The mature sporophyte (tree) makes make and female cones. The pollen cones have microsporangia and microsporangium then go through meiosis to make pollen that arrives before the megasporangium has gone through meiosis. The ovulate cone then goes through meiosis (from here 1n) and then the sperm comes in and fertilizes the egg (back to 2n). Then it’s an embryo to a seedling and back to a mature sporophyte.
How does the pollen get to the female cone?
Wind. Because of this they make a lot of pollen to increase their success chances.
Megagametophyte (conifers)?
Makes egg in archegonium and nourishes the embryo.
Mircogametophyte (conifers)?
Pollen grain(makes sperm).
How does the conifer seen have 3 generations?
Seed coat (2n from parent generation). Megagametophyte (1n 1st gen). Embryo is the new sporophyte (2n 2nd gen).
Male cones
Shorter lived and smaller
Female cones
Start as soft pink small cones. Take a year or two to fully develop.
Gymnosperms
Naked seeds. Conifers have them.
How are conifer very slow in reproduction?
Year 1: Initiate male and female cones.
Year 2: Male meiosis to make pollen, pollination, female meiosis after pollination.
Year 3: Fertilization, mature seeds.
What is required to open the cones so the seeds will be released?
Wildfires. No fire = no reproduction.
