Kingdom Plantae - Introduction and Alternation of Generations

Characteristics of Kingdom Plantae

• posses waxy cuticle

• stomata

• multicellular

• eukaryotic

• photoautotrophs

• chlorophyll a & b and carotenoids

• store food in the form of starch

• cellulose cell wall

• embryo remains protected in female body

Which of these features enabled them to survive on land

• waxy cuticle

• water loss only through stomata or lenticels

• embryo remains protected inside female body (Protects embryo from drying out and harsh land conditions)

Evidence to support that plants originated from algae

• same photosynthetic pigments

• cellular cell walls & plasmodesmata

• reproduce by fragmentation

What is the ‘Alternation of Generations’

• plants alternate between a diploid and haploid organism

Describe the ‘Alternation of Generations’

1. Sporophyte (the body of what we usually think of is a fern)

2. Sporophyte makes sporangium to house the spores

3. From the sporangium spore mother cells (precursor to spores) divide by meosis to form spore

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4. Spores are then distributed and form gametophytes

5. Gametophytes (produce gametes), from the antheridium (SPERM) and archegonium (OVA) in the gametophyte the gametes are produced

6. Gametes meet by chemotaxis and fuse → fertilization

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7. Fertilization results in a zygote

8. Zygote then ‘grows up’ and becomes the sporophyte

Why did the dominant generation in land plants shift from gametophyte to sporophyte?

• Having two sets of chromosomes makes it more mutation resistant, grow larger, have vascular tissue, protect embryos, and spread spores better—making them better suited for life on land.

How did plants evolve to become more successful at colonizing terrestrial environments

• external fertilization → internal fertilization which requires no water

• vascularization → better transport and support

• homospory → heterospory (differentiated male and female spores)

• embryo → seed capable of germinating even years after unfavorable conditions