Transcript Plants - cayugascience

Kingdom Plantae
The Shift to Land
 Hypothesis that green algae are the
closest evolutionary relatives of land
plants based on
Presence of chlorophyll a and b
Cellulose cell walls
Store food in form of starch
Similarities in genetic code
 However there are key differences
Adaptations to Life on Land
 Since plants live in terrestrial environments,
need protection from drying and system to
transport water and nutrients
 Plants only evolved from aquatic to terrestrial
environments 460 million years ago
Reproduce using embryos (spores in
algae)
Development of vascular tissue,
seeds and flowers
Vascular tissue, leaves and
roots
 First land plants were small and simple and did
not have vascular tissue; eventually evolved to
vascular plants
 Vascular tissue allowed evolution of roots
 Allowed anchoring
 Absorb and transport water
 Increased range of plants into drier environments
 Leaves came next
 Increased surface area of plant allowed better
exchange of gases involved in photosynthesis and
light capture
General Characteristics
 Use photosynthesis to gain energy, therefore
autotrophic.
 Live in all aquatic and terrestrial habitats
except at the poles.
 Through photosynthesis plants take in carbon
dioxide and provide oxygen for the
environment.
 Three main parts of the plant are root, stem
and leaves.
General characteristics cont.
 Roots - penetrate the soil to anchor the plant and reach
sources of water
 Leaves - provide a greater surface area for
photosynthesis
 Stem - supply rigid tissues that raise and support the
leaves
 Vascular tissue acts like a circulatory system and
transports water, nutrients, and dissolved minerals to all
parts of the plant
 A seed is a structure made up of an embryo, stored food
and tough waterproof coat
 Life cycle consists of two generations which alternate
between a haploid gametophyte and diploid sporophyte
stage.
Classification of Plantae
 Although there are a
vast variety of plants
(over 300,000 known
species) in the world,
they can all be placed in
one of four main groups
based on vascular tissue
and seeds.
 Each large group
contains several
divisions, which are the
rough equivalent to a
Phylum.
Classification of Plants
 Bryophytes (mosses)
 non-vascular, seedless
 Ferns
 vascular, seedless
 Gymnosperms (conifers)
 vascular, non-enclosed seeds
 Angiosperms (flowering plants)
 vascular, enclosed seeds
1) Non-Vascular Plants
(Mosses and their relatives)
 Three divisions (mosses, hornworts and liverworts).
 No vascular tissue, so depend on osmosis and
diffusion to transport nutrients.
 Usually grow in dense mats of low tangled vegetation
that can hold water like a sponge, allowing them to
survive cold or dry periods.
 Have no roots, instead have root-like rhizomes which
are small root like structures
 Sexual reproduction.
Non-vascular Plants
Mosses (Bryophytes)
 Very successful and widespread, thrive in such diverse
habitats as bogs, tundra, on bare exposed rocks, and in
deep shade.
 Twice as many species of mosses as there are mammals!
 Sporophytes do not contain chlorophyll
Liverworts (Hepatophytes)
 Grow flat, low to the ground and are rarely more than 30
cells thick.
 80% are leafygametophytes that resemble mosses. Live in
tropical forests and in humid climates.
 20% have gametophystes with flattened, lobed bodies
called thalli that resemble the lobes of animal’s livers.
 Many small chloroplasts per cell.
Non-Vascular Plants cont.
Hornworts (Anthocerophytes)
 Broad, flat
 Usually blue-green in colour.
 Sporophyt looks like mini-green cattle
horns
 One large chloroplast per cell
2) Seedless Vascular Plants (Ferns
and their relatives)
 Originated about 300 million years ago
 developed vascular tissue that allowed them
to grow tall
 Sporophyte (diploid) generation becomes
dominant stage in life cycle
 Gametophytes are short-lived and require
moisture to carry out sexual reproduction
Seedless Vascular Plants
Whisk Ferns (Psilotophytes)
 Look like small green whisk brooms
 No leaves or roots
 Short rhizomes, which are horizontal,
underground stems.
 Produce spores.
Club Mosses (Lycopodophytes)
 Small evergreen-looking plants that grow in
dense mats in moist temperate or tropical
forests.
 Not related to true mosses!
 Have true roots and stems.
Horsetails (Sphenophytes)
 Once included tree-sized members, but now just smaller
plants (1 m).
 Often found in damp areas or along roadsides.
 Can be used to scour pots.
 Have silica in their cells, which accounts for the roughness.
 Can be made into a shampoo to combat head lice.
Ferns (Pteridophytes)
 Dominated the forests during the Carboniferous period (315280 mya).
 Most familiar and successful of the seedless vascular plants.
 Have roots, stems, a waxy epidermis that reduces water loss
by evaporation and stomata in their leaves for gas
exchange.
 Ferns produce millions or even billions of spores in their
lifetime.
 Have fronds, which are seed leaves that grow up from
rhizomes.
3) Gymnosperms (Conifers)
 disperse by means of seeds
 reproduce sexually without needing water and different
than other 2 groups.
 have seeds that are exposed on the surface of cone scales
 gymnosperm means ‘naked seed’
 includes cone-bearing trees: pines, firs, spruce, yew,
cedars, redwood and many other large trees.
 Also includes the cycadophytes, gnetophytes and
ginkgophytes.
3) Gymnosperms
Conifers
 Largest group of gymnosperms. Form vast forests in the
colder regions of the world


Covering of bark helps protect the stem and reduce water
loss.
Have a pyramidal shape and flexible branches to help snow
and ice slide off the tree reducing branch breakings.

needle like leaves have a thick, waxy cuticle and sunken
stomata, which reduce the rate of evaporation.

Most conifers are evergreens, so they continually lose and
replace their needles all year round.
Better able to grow in nutrient poor soils because they do
not need to grow a complete set of leaves all at once.

Gymnosperms cont.
Gnetophyta
 Very rare, found in southern Africa
 May live 100 years. Produces two broad leaves that it
keeps its entire life.
Cycadophyta
 Short, palm-like trees with scaly trunks. Mainly exists
in the tropics. Common trees when dinosaurs roamed
the earth.
Ginkgophyta
 Distinctive lobed leaves.
 The only living species is Ginko biloba, which was
common during the Jurassic period (200 mya).
 Cultivated in Asian temples for hundreds of years, which
helped protect against extinction.
4) Angiosperms (Flowering
Plants)
 Plants that protect their seeds within the body of a fruit
are called angiosperms or flowering plants.
 Include vines, grasses, shrubs, trees and water plants.
 Grow almost everywhere on land from tundra to
tropics.
 Flower contains sexual reproductive structures, use
wind, water, animals, bats, birds and insects as pollen
carriers.
 Divided into monocots (1 seed leaf) and dicots (2 seed
leaves). Seed leaves (cotyledon nourish the growing
embryo
 Appeared on earth more than 150 mya. More than ¾
of all species of living plants!
Monocots vs. Dicots
http://www.ted.com/talks/jonathan_drori_the_beautiful_tricks_of_flowers.ht
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