Unit 6 – Lecture 6

Alternation of Generationstype of reproduction

utilizing asexual & sexual means

Alternation of Generationsoffspring generations

alternate between being haploid [1n] in one generation to being diploid [2n] the next.

Alternation of Generationsin some plants, the

sporophyte is a completely different plant than the gametophyte.

in others, the gametophyteis something we really don’t see.

Alternation of GenerationsSporophyte [2n]

produces spores [1n]through meiosissporophyte is the

typical “adult plant” that we see

Alternation of GenerationsSpores [1n] produce

gametophytes [1n] throughmitosis

Alternation of GenerationsGametophyte [1n]

produces gametes [1n]through mitosis

Alternation of GenerationsGametes [1n] fuse

in fertilization to produce zygote [2n]

Alternation of GenerationsZygote [2n] grows to

become embryo [2n]

Alternation of GenerationsEmbryo [2n] grows

to become sporophyte [2n]…

etc.

Alternation of Generationsnon-vascular and non-seed plants MUST have

water to reproduce.flagellated sperm must swim to egggametophyte can be very

small, but visible – 1cm or less.

Other Asexual Reprod Methodsvegetative reproduction – new plant forms

from existing plant part (roots)

fragmentation – new plant forms from a cutting of the original plant.

Seed Plantsare vascular…two varieties:

gymnosperm – produce conesangiosperm – produce flowers

Angiospermsproduce flowers and seeds inside of a fruit

petals, pistil, stamen, etc.petals attract pollinatorsfruit attracts organisms which can spread

seeds

Angiosperms

Angiosperms

Angiospermsare either monocot or dicot

cotyledon – the seed “leaves” or sides / food supplies

don’t need to know these directly:have different types of xylem & phloemhave different types of veinationhave differences in petal arrangement

Seed Production

Germinationgermination – zygote growing into new plant

requirements: watersuitable temperatureoxygentime

Germinationgermination – zygote growing into new plant

requirements: light other:

freezing – applessoaking in salt water – coconuts

fire – many conifers

cannot be halted