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Plants. Origins of Plants A. Plants most likely evolved from filamentous green algae that lived in ancient oceans 1. evidence includes: * both have cell walls that contain cellulose * have same types of chlorophyll * store food as starch. B. Adaptations for life on land

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Origins of Plants

A. Plants most likely evolved from filamentous green algae that lived in ancient oceans

1. evidence includes:

*both have cell walls that contain cellulose

* have same types of chlorophyll

* store food as starch


B. Adaptations for life on land

1. waxy coating covers leaves, stems, fruit- called the cuticle

2. early plants were simple in structure-the leaf was an adaptation & is where photosynthesis occurs

3. roots- this adaptation allows plants to take in nutrients & water from the soil, anchors plants to ground


4. stem- organ that provides support for growth & helps transport food & water from roots to leaves

a. stems of most plants contain tubelike cells that makeup vascular tissues- these tissues transport water & nutrients in vascular plants

b. ex: of vascular plants include pine trees, ferns, sunflowers


c. mosses & other small plants are nonvascular- they don’t have vascular tissues because their bodies are only cells thick so water can travel from cell to cell

d. the evolution of vascular tissues was important because

* allowed plants to survive on many habitats

* live farther away from water

* can grow much larger due to fibrous tissues


5. Reproduction on land

a. seed was important as it contains as embryo & its food supply, covered by protective coat

b. in non-seed plants (mosses & ferns), sperm need film of water to reach egg


6. Lives of plants include 2 stages

a. gametophyte stage – development of haploid gametes

b. sporophyte stage- begins w/fertilization, all cells are diploid spores produces by meiosis are haploid


II. Classification of Plants

A. Non seed plants

1. non seed plants- produce hard walled reproductive cells called spores, can be vascular or non-vascular

2. Include nonvascular plants:

a. hepaticophyta: liverworts b. anthocerophyta: hornworts

c. bryophta: mosses

d. psilophyta: whisk ferns


3. Include vascular plants:

a. lycophyta: club mosses

b. arthrophyta: horsetails

c. pterophyta: ferns


B. Seed Plants

1. produce seeds, which is more effective way to reproduce in a dry environment than using spores

2. Many divisions

a. Cycads -palmlike trees, male/female on separate tree

b gnetophyta-found mostly in deserts, small shrubby plants, vines

c. ginkoes -trees that lose leaves in the fall, have male & female on separate tree

d. conifers -pine, spruce, etc; seeds in cones,

e. anthophytes-the flowering plants; all have flowers from which fruit with seeds are produced, include tomatoes, roses, apples, grass, grapes- most diverse, over 250 000 species


* divided into two groups: monocotyledons and dicotyledons

CHAPTER 22 The Diversity of Plants

I. Nonvascular plants

A. Characteristics

1. not as common- require close association with water for photosynthesis & reproduction

2.lack of vascular tissue limits plant size

B. Generation alteration

1. life cycle alternates bwtn diploid sporophyte & hapliod gametophyte


2. sporophytes grow attached to and dependent on gametophytes to take in water

3. gametophytes of nonvascular plants have 2 reproductive structures

a. antheridium- male structure, sperm are produced

b. archegonium- female structure, eggs produced

c. fertilization, which begins the sporophyte generation, occurs in the archegonium


C. Non- Seed Vascular Plants

1. these vascular plants have the vascular tissue, but don’t form seeds for reproduction

2. alternation of generations- spore producing generation is dominant and larger in size than the gametophyte, and doesn’t depend on the gametophyte for water or nutrients

3. leaves were a major advancement- protect the developing spore cells


4. strobilus- structure that holds spores that when released, form the gametophyte or prothallus, which will release sperm and fertilize eggs using water to form a dominant sporophyte

D. Seed Plants

1. spores are produced by the sporophyte generation

2. these spores develop into the male & female gametophyte

a. male gametophyte develops inside a pollen grain that includes the sperms cells, nutrients and protective outer coating


b. Female gametophyte is contained in the sporophyte structure call an ovule

3. the union of the egg and sperm form the sporophyte zygote

a. the zygote develops into an embryo

b. the embryo has a cotyledon, or structure that stores food for the embryo

c. embryos of seed plants are grouped by how many seed leaves the cotyledon has

* monocot- 1 seed leaf, flower parts in threes

* dicot- 2 seed leaves, flower parts in fours & fives


4. Types of Seed Plants

a. Conifers- small needle is modified leaf

b. most are evergreen, keeping leaves year round

c. some are deciduous- lose leaves in fall as an adaptation to reduce water loss (plant must become dormant since it can’t photosynthesize w/o leaves)

d. angiosperms -flowering plants

5. Life spans

a. annual- live for 1 year or less

b. biennial- live for 2 years

c. perennials- live for several years