Biology Of Plants 3

Front 1

key advances

Back 1

1. independend sporophyte gametophyte develop at least partially while attached to sporophyte

2. Water is no longer required for fertilization

3. pollen

Front 2

seed is

Back 2

mature ovule containing an embryo + 2 layers of tissues (integuments)

Front 3

Events leading up to the evolution of the ovule

Back 3

Megasporangium stopped releasing spores

Reduction to one megaspore mother cell per megasperangium (before meiosis)

One surviving megaspore(1 of 4 after meiosis)

Female gametophyte Retained inside the sporophyte, no longer free living

Integuments surround the megasporangium(slim opening-micropyle)

Megasporangium was modified to recieve the microspores(pollen grains)

Front 4

spores vs seeds

Back 4

All spores are single celled, seeds are all multicellular

Spores are dispersed through wind or gravity, seeds are dispered by wind, gravity, but also by water, animals, etc.

Spores go dormant versus harse conditions, seeds have variable dormaancy (days -> decades)

Simple form/ structure in spores, more complexity in seeds

Spores are haploid(n), seeds → 2n in n in 2n

Front 5

Seeds (3 generations of tissues)

Back 5

(2n)embryo(new sporophyte generation)

(n)endosperm(nutrition source)(gametophyte stage)

(2n)Seed coat - develops from the integument (part of a cone from the parent sporophyte)

Front 6

pollen

Back 6

- microsporangium → male microgametophytes(pollen grain- still released from parent plant

Can survive harsh conditionsPlants are no longer tied to water for transfer of gametes

No longer have flagella on sperm produced, 2 sperm cells per pollen grain

Front 7

female cones

Back 7

Woody cones

Consists of many megasporangiaMake megaspores(retained by the plant)Grow into megagametophytesProduces archegonia( produce eggs)

Hundreds of eggs produced per cone

Front 8

male cones

Back 8

Typically not woody

Consist of many microsporangiaMicrosporesmicrogametophytes(pollen grain)

Millions of pollen grains per cone

Front 9

Pollination

Back 9

1. Pollen tube forms

2. Two sperm releasedFertilizes the egg, the other breaks down

3. Embryo is produced (2n)

4. Growth is suspended