Plants Lesson 2 Flashcards
(67 cards)
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