Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Evolution of...

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies

Evolution of Plants

Chapter 16

Copyright © McGraw-Hill Companies Permission required for reproduction or display


Outline

• Adapting to Terrestrial Life• Vascular Plants• Seedless Vascular Plants • Seed Plants

Gymnosperms Angiosperms

- Flowers Dicots and Monocots Seed Dispersal


Adapting to Terrestrial Living

• Green algae that were probably the ancestors of today’s plants are aquatic organisms not well-adapted to living on land. Had to overcome three challenges:

- Minerals absorption from rocky surfaces- Water conservation- Reproduction on land



• Mineral Absorption Plants require relatively large amounts of

six inorganic minerals:- Nitrogen, potassium, calcium,

phosphorus, magnesium, and sulfur. Mycorrhizae

• Water Conservation Cuticle - watertight outer covering.

- Stomata - gas and vapor exchange.



• Reproduction on Land Due to immobility, gametes must avoid

drying while they are transferred by wind or insects.

- Spore Development Generation alteration

- Sporophytes - diploid generation- Gametophyte - hapolid generation


Generalized Plant Life Cycle



Evolution of Vascular System

• Terrestrial plants are required to carry water up from roots to leaves, and carbohydrates down from leaves to roots. Vascular System

- Specialized strands of connected hollow cells.

Nine of Twelve living plant phyla are vascular.


Nonvascular Plants

• Only two phyla of living plants lack a vascular system: Liverworts (Hepaticophyta) Hornworts (Anthocerophyta)

• Simple Vascular Systems Mosses were first plants to evolve strands

of specialized conduction cells.- No specialized wall thickening.


Moss Life Cycle


Evolution of Vascular Tissue

• Appeared approximately 430 mya. Grew by cell division at the tips of stem

and roots (Primary Growth).• About 380 mya vascular plants developed a

growth in which a cylinder of cells beneath the bark divides, producing new cells around plant’s periphery (Secondary Growth). Necessary for tall trees with thick trunks.


Leaf Vascular System



Seedless Vascular Plants

• Most abundant of the four phyla of seedless vascular plants contain ferns with about 12,000 living species. Have both gametophyte and sporophyte

individuals, each independent and self-sufficient.

- Gametophyte produces eggs and sperm.- Sporophyte bears and releases hapolid

spores.


Fern Life Cycle


Seed Plants

• Seed - Embryo cover that offers protection of embryonic plant at its most vulnerable stage. Male and Female gametophytes

- Male - microgametophytes (pollen grains) arise from microspores.

- Female - megametophytes contain eggs and develop from megaspores produced within ovule.

Pollination - transfer of pollen.


Seed Plants

• Five living phyla of seed plants: Four are gymnosperms - ovules not

completely enclosed by sporophyte tissue at time of pollination.

Fifth is angiosperms - ovules completely enclosed by vessel of sporophyte tissue (carpel) at time of pollination.


Seed Structure


Seed Plants

• Adaptive value of seeds: Dispersal

- Facilitate migration and dispersal Dormancy

- Wait for favorable conditions Germination

- Synchronization with environment Nourishment

- Energy source for young plants


Gymnosperm Phyla

• Coniferophyta (Conifers) Trees that produce seeds in cones.

- Most familiar of four gymnosperm phyla.- Seeds develop on scales within cones

and are exposed at time of pollination.• Cycadophyta (Cycads)• Ginkgophyta (Ginkos)• Gnetophyta (Gneetophytes)


Conifer Life Cycle


Rise of Angiosperms

• Comprise 90% of all living plants. Use roots to anchor plants in one place to

obtain nutrients. Produce tiny male gametes that are easily

transported.• Flower - reproductive organs that employ

bright colors to attract pollinators and nectar to induce entrance into the flower to contact pollen grains.


Flowers

• Structure consists of four distinct whorls: Outermost - Protects flower from physical

damage (sepals). Second - Attracts pollinators (petals). Third - Produces pollen grains (stamens

and anther). Fourth - Produces Eggs (Carpel)

- Ovary- Style- Stigma


Angiosperm Flower


Why Different Kinds of Flowers

• Different pollinators are attracted to specific types of flowers. Bees most numerous insect pollinators.

- Becomes coated with pollen while inside the flower.

Butterflies Moths Hummingbirds



Double Fertilization

• Angiosperms produce a highly nutritious tissue (endosperm) within their seeds. Male gametophyte contains two sperm.

- Second fuses to form endosperm cell (double fertilization).

Dicotyledons - Embryos with two seed leaves.

Monocotyledons - Embryos with one seed leaf.


Angiosperm Life Cycle


Dicots and Monocots


Seed Dispersal - Fruits

• Fruit - mature, ripened ovary containing fertilized seeds, surrounded by a carpel. Fleshy fruits encourage predation.

- Berries - Many seeded forms on inner carpel wall. (Grapes, Tomatoes)

- Drupes - Stony inner layer adhering to single seed. (Peaches, Olives)

- Pomes - Fleshy portion comes from petals and sepals. (Apples, Pears)


Review

• Adapting to Terrestrial Life• Vascular Plants• Seedless Vascular Plants • Seed Plants

Gymnosperms Angiosperms

- Flowers Dicots and Monocots Seed Dispersal

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Evolution of...

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