Lecture 2- Major Groups of Land Plants and their Reproduction Flashcards
How many divisions are there of land plants
10
General life cycle of animal
gametes, fertilization/syngamy— zygote(2n)—- multicellular adult (2n)—- meiosis—- gametes
General life cycle of plant
gametophyte makes gametes
two gametes unite to produce zygote
zygote undergoes mitosis to become sporophyte
sporophyte undergoes meiosis to produce spores
spores develop into gametophyte via mitosis
Meiosis in land plants
produces spores
mitosis in land plants
produces gametes
Four major groups of land plants
Mosses, ferns, conifers, angiosperms
Mosses
- Division byophyta
- 15,000 species
- damp areas, swimming sperm and no vascular tissue
- no true leaves
- gametophyte dominant
- homosporous
Moss gametophytes
- make gametes
- haploid
- little projections
- make either egg or sperm, not both
Moss sporophytes
- arise from the gametophyte
- short lifespan, disintegrate after they release spores
Life cycle of a moss
1- Males: haploid spore develops into protonemata
protonemata develops into male gametophyte antheridia that makes sperm
Females: spore develops into female gametophyte, archegonia. Makes egg
- Sperm gets in water. Sperm lands on female gametphye archegonium and swims down. Fertilizes the egg to produces diploid cell, zygote
- Diploid cell undergoes mitosis to develop into a sporophyte. Sporophyte arises out of gametophyte
- Sporophyte undergoes meiosis to produce spores. Releases spores and sporophyte disintegrates
Spores
- haploid
- not a gamete because they don’t unite
Non vascular plants
- limited
- not morphologically diverse
- bryophytes
- gametophyte dominant
Vascular plants
- sporophyte dominant
- xylem and phloem
- tracheophytes
- cell walls with lignin, allows growth in tall
vascular tissue
xylem and phloem
xylem
- controls water and mineral flow
- to inside
- tracheids
phloem
- transports sugars
- to outside
Ferns
- division pterophyta
- 20,000 species
- appeared approx 400mya
- ptero: means wing or feathered
- vascular plants
- sporophyte dominant
- swimming sperm
- homosporous or heterosporous
Life cycle of a fern
1- Sporangium release spores that develop into bisexual photosynthetic gametophyte
2- Each gametophyte has Antheridia makes sperm, archegonia makes egg
3- Water transmits sperm, fertilizes egg in archegonia to produce diploid zygote
4- Zygote develops into sporophyte, sporophyte takes over and gametophyte withers away
5- On sporophyte are sorus that contains clusters of sporangium. Sporangium undergoes meiosis to produce spores
6- Sporangium releases spores
sorus
cluster of sporangium
sporangium
- where spores produced
- diploid structure that makes haploid sperms
- produces 64
- releases spores
Homospory
-makes one size spore
-all mosses, most ferns
Sporangium produces single size spore, spore develops into typically bisexual gametophyte, gametophyte produces egg and sperm
Heterospory
Megasporangium produces 4 spores, surviving one is megaspore, megaspore turns into female gametophyte (archegonium), produces egg
Microsporangium produces microspores, microspore turns into male gametophyte antheridia, makes sperm
Difference between male and female in all life
- size of gametes
- female has bigger gametes
- male has smaller gametes
difference between mosses and everything else
-vascular tissue
5 divisions of seed plants
1- Cyanophyta 2-Gingkophyta 3-Gnetophyta 4-Coniferophyta 5-Anthophyta
Seed plants
seed and pollen
Seed
- embryo, nutrition, seed coat
- develops from ovule
ovule
Novel structure appearing in seed plants
Site of meiosis for female
Contains female gametophyte, female sex organs, egg and embryo
The megasporangium, megaspore, and their integument(s)
Inside each ovule, a female gametophyte develops from a megaspore and produces one or more eggs
Integument
A layer of sporophyte tissue that envelops and protects the megasporangium
Ovule development
a) Unfertilized ovule
The micropyle: the only opening through the integument, allows entry of a pollen grain
b) Fertilized ovule
A megaspore develops into a female gametophyte, which produces an egg
The pollen grain, which has entered through the micropyle, contains a male gametophyte
The male gametophyte develops a pollen tube that discharges sperm, therefore fertilizing the egg
c) Gymnosperm seed
Fertilization initiates the transformation of the ovule into a seed
Consists of a sporophyte embryo, a food supply, and a protective seed coat
The megasporangium dries out and collapses
Contains multiple generations
Seed coat: Parental Sporophyte generation
-Female gametophyte: Haploid generation
- New zygote: 3rd generation
Female gametophyte- bagged lunch
Seed nourishes young offspring with haploid gametophyte tissue
Pollen
IS NOT SPERM
Is the male gametophyte in seed plants
Contains sperm
Seed plants only develop if ovule is fertilized
The conifers
-division coniferophyta
-550 species
-reproductive organs in cones: both male(pollen)and female (egg)
Naked seeds “gymnosperms”: seed sits there as an ovule, nothing else around it
Seed: embryo nourished by megagametophyte
Slow reproduction (see jack pine)
Sporophyte dominant
Heterosporous
Microgametophyte= pollen
Megagametophyte
-Within ovule
-Makes egg and then nourishes embryo
Life cycle of conifer
- Each conifer tree has both male and female cones
- Male cones make diploid microsporocytes (before meiosis) in microsporangium. Microsporocytes divide by meiosis, producing haploid microspores. Microspores develops into a pollen grain: a male gametophyte enclosed within the pollen wall, spread by the wind
- A female cone projection has two ovules, each containing a megasporangium: Megasporocyte undergoes meiosis, produces 4 haploid products, only 1 survives which is called the megaspore
- The megaspore develops into a female gametophyte by mitosis that contains one, two or three archegonia, each which will form an egg
- Pollen forms pollen tube that digests its way through the megasporangium
- Fertilization occurs when sperm and egg unite
- Fertilization usually occurs more than a year after pollination. The ovule becomes a seed, consisting of an embryo, food supply and seed coat
Megagametophyte in conifers
Makes egg in archegonium
Nourishes embryo
Microgametophyte in conifers
-pollen grain, makes sperm
