Transcript Diversity and Adaptations of Plants

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
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– Absorb nutrients from surroundings
– Prevent water loss
– Reproduce without water in the
environment
Absorbing nutrients
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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
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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.
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Reproducing on land
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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
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Vascular Tissues - elongated tube-like cells
– Leaf – broad flat structure that traps light energy
for photosynthesis
– Stem – provides:
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Structural support
Transports food, water, and other materials
– Roots - structures that
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Acquire water and nutrients from soil
Transport water and nutrients to stem
Anchor plant to ground
Some roots also store starch
More Adaptations
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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
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Alternation of Generations
– All plants have two life-cycle generations
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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
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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
Lunularia cruciata
Polytrichum commune
Anthoceros
Seedless Vascular
Plants
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Have a vascular system
– Grow larger than non-vascular plants
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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
Wisk Fern
Club Moss
Fern w/ Fiddle Heads
Horsetail: Equisetum
hymale
Seed Plants:
Gymnosperms
(Naked Seed)
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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
Conifer
Ginko biloba
Seed Plant:
Angiosperms
(Flowering)
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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
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Seeds have an endosperm (a stored food supply)
Two Types:
– Monocots
– Dicots
Monocots
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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
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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