Diversity and Adaptations of Plants

Plants became established on land

Probably evolved from multi-cellular aquatic green algae (a protist)

Plants had to do three things to survive on land– Absorb nutrients from surroundings– Prevent water loss– Reproduce without water in the

environment

Absorbing nutrients Aquatic algae and

aquatic plants take nutrients directly from water (diffusion and osmosis)

Early plants and fungi developed symbiotic relationships to help plants get nutrients from rocks and soil.– Ex. Mycorrhizae

mycos = fungi rhiza = root

Preventing water loss Developed a cuticle –a waxy layer

water proof coating on stems and leaves.

This barrier prevents water in a plant’s tissues from evaporating into the atmosphere.

Reproducing on land Sperm of algae can swim through water b/c

lives in an aquatic environment Most land plant sperm must move without

water Sperm is enclosed in structures to keep

them from drying out.– These structures are called pollen– Pollen can be carried by wind or animals

Other Adaptations Vascular Tissues - elongated tube-like cells

– Leaf – broad flat structure that traps light energy for photosynthesis

– Stem – provides: Structural support Transports food, water, and other materials

– Roots - structures that Acquire water and nutrients from soil Transport water and nutrients to stem Anchor plant to ground Some roots also store starch

More Adaptations Reproductive Structures

– Seed – contains an embryo, food supply, and a protective coat

Protects the zygote or embryo from desiccation (drying out)

Aids in dispersal

– Flower – reproductive structure that produces pollen and seed

Makes plant reproduction more efficient Can be male, female, or hermaphroditic

Plant Life cycles Alternation of Generations

– All plants have two life-cycle generations Gametophyte (n) – produces the gametes(n) by

mitosis Sporophyte (2n) – produces spores(n) by meiosis

– The gametes fuse to form a diploid zygote which develops into a new sporophyte; thus the sporophyte and gametophyte alternate.

Life Cycle of Mosses Mosses reproduce sexually by forming spores.

                  

A single moss "plant" is a gametophyte (n). Sperm (n)

from one gametophyte fertilizes the egg of another,

producing a zygote (2n).

                     

A stalk-like structure, called a Sporophyte (2n), with a

capsule at the top containing the spores (n) grows from the

zygote.

Survey of the Plant Kingdom: Non-Vascular

Plants Nonvascular plants – do not have a

vascular system– Simple and small in size

Water and other materials transported by osmosis and diffusion

– Larger gametophyte Rhizoids anchor the gametophyte to ground

– Require water for sexual reproduction– Examples: mosses, liverworts, hornworts

Polytrichum commune

Lunularia cruciata

Anthoceros

Seedless Vascular Plants Have a vascular system

– Grow larger than non-vascular plants Larger sporophyte, while smaller

gametophyte develops on or below surface of soil

Still need water to reproduce Drought resistant spores Examples:

– Ferns, Club Mosses, Horsetails, and Wisk Ferns

Club MossFern w/ Fiddle Heads

Horsetail: Equisetum hymale

Wisk Fern

Seed Plants: Gymnosperms (Naked Seed)

Seed plants whose seed does not develop within a fruit (sealed container)

Greatly reduced male (pollen) and female gametophyes. Develop within male and female cones.

Wind pollination Examples:

– Conifers, Cycads, Ginkos, Gnetophytes

Encephalartos lehmannii Ginko biloba

Conifer

Seed Plant: Angiosperms (Flowering)

Have flowers where the male and female gametophyte develops.

Produce seeds enclosed in a specialized structure called a fruit– Fruits provide some protection but mostly aid in seed

dispersal Seeds have an endosperm (a stored food supply) Two Types:

– Monocots– Dicots

Monocots Produce seeds with one seed leaf

(cotyledon) Flower parts are in multiples of 3 Long narrow leaves with parallel

veins Vascular bundles scattered Examples: Tulips, Irises, Wheat,

Corn, Rice

Dicots

Seeds with two seed leaves (cotyledons)

Flower parts in multiples of two’s, fours, fives

Leaves with branching or netted veins

Vascular bundles form a ring

Examples: daisies, sunflowers, lettuce, roses, apples, potatoes