1. Bellwork: What makes a plant a plant
Bellwork: What makes a plant a plant? Describe the general life cycle of a plant

2. What is a plant?
Section 22.1

3. What do plants need to survive?
Plants form part of the kingdom Plantae
Cell wall containing cellulose
Photosynthesize using chlorophyll a and b
Most are autotrophs, a few are parasites or saprobes
Plants need Sunlight
Required to carry out photosynthesis
Plants needs to exchange gas
Oxygen for cellular respiration
Carbon dioxide for photosynthesis
Issue is to exchange gasses and not loose too much water at the same time
Plants need water and minerals
Plants essentially sweat
Plants have evolved to limit water loss and speed up uptake from the ground
Minerals in the soil are needed for plant growth

4. How have plants adapted to life on land?
It is thought that all land plants originated in the water
Most photosynthetic organisms were unicellular eukaryotes, similar to today’s green algae
Confused evolutionary biologists at first – how can algae and an oak tree be in the same kingdom?
Cell walls and photosynthetic segments are the same! Have the same reproductive cycles
Genomes are also closely related

5. The first land plants
Fossil spores of land plants have been dated to 475 million years ago
No actual plant fossils
Oldest fossilized land plants are approximately 425 million years ago
No leaves and roots, only a few cm tall
Difficulty obtaining water
Growed close to the ground in damp locations
Plants evolved to be more resistant to the drying rays of the sun, capable of conserving water and reproducing without water
Emergence changed land, changed ecosystems
Many groups developed – mosses, ferns, cone bearing plants and flowering plants
Adapted differently to a range of terrestrial environments

6. The plant kingdom
Can be divided into five major groups based on four important features
Embryo formation
Specialized water conducting tissues
Seeds
Flowers

7. What defines most plant life cycles?
The life cycle of land plants has two alternating phases – a diploid phase and a haploid phase
Alternation of generations
Sporophyte – multicellular diploid phase
Gametophyte – multicellular haploid phase

8. Trends in plant evolution
Gametophyte size has decreased and sporophyte size has increased
Most green algae have a diploid sporophyte phase, some don’t
Only multicellular bodies are gametophytes
Ferns and their relatives have a small gametophyte and a larger sporophyte
Seed plants have an even smaller gametophyte which is contained within sporophyte tissues.

9. Key point questions What do plants needs to survive?
How did plants adapt to life on land?
What features define most plant life cycles?
How have plants in general changed over time?