KEY CONCEPT Plant life began in the water and became adapted to land.

1
KEY CONCEPT Plant life began in the water and
became adapted to land.
2
Land plants evolved from green algae.

• Plants and green algae have many common traits.

• both are photosynthetic eukaryotes
• both have the same types of chlorophyll
• both use starch as a storage product
• both have cell walls with cellulose

3

• Genetic analysis points to the common ancestor
  of all plants.

• extinct green algae species in class
  Charophyceae
• modern charophyceans common in lakes and ponds

4

• Important plant characteristics likely originated
  in charophyceans.

• multicellular body allowing for specialization of
  cells and tissues

• cell division that allows for chemical
  communication between cells
• reproduction involving sperm swimming to egg

5

• True plants evolved through natural selection.

• Ancestral charophyceans lived in areas of shallow
  water.

• Those that could survive longer dry periods were
  favored.
• First true plants probably grew at edges of
  water.
• True plants have embryos that develop while
  attached to female parent.

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• True plants evolved through natural selection.

7
Plants have adaptations that allow them to live
on land.

• Challenges of living on land have selected for
  certain plant adaptations.
• A cuticle allows plants to retain moisture.
• waxy, waterproof layer

• holds moisture in

8

• Stomata are tiny holes in the cuticle.

• can open and close
• allow air to move in and out

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• A vascular system allows resources to move to
  different parts of the plant.

• collection of specialized tissues

• brings water and mineral nutrients up from roots

• disperses sugars from the leaves
• allows plants to grow higher off the ground

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• Lignin allows plants to grow upright.

• hardens cell walls of some vascular tissues
• provides stiffness to stems

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• Pollen grains allow for reproduction without
  free-standing water.

• pollen grains contain a cell that divides to form
  sperm
• pollen can be carried by wind or animals to
  female structures

12

• A seed is a storage device for a plant embryo.

• seed coats protect embryos from drying wind and
  sunlight
• embryo develops when environment is favorable

13
Plants evolve with other organisms in their
environment.

• Plants and other organisms can share a
  mutualistic relationship.
• a mutualism is an interaction in which two
  species benefit
• plant roots and certain fungi and bacteria
• flowering plants and their animal pollinators

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• Plants have adaptations that prevent animals from
  eating them.

• spines and thorns

• defensive chemicals