Transcript 20.2 Classification of Plants

20.2 Classification of Plants
KEY CONCEPT
Plants can be classified into nine phyla.
20.2 Classification of Plants
Mosses and their relatives are seedless nonvascular
plants.
• Nonvascular plants grow
close to the ground to
absorb water and nutrients.
• Seedless plants rely on freestanding water for
reproduction.
• Liverworts belong to phylum
Hepatophyta.
– often grow on wet rocks
or in greenhouses
– can be thallose or leafy
20.2 Classification of Plants
• Hornworts belong to phylum Anthocerophyta.
– found in tropical forests and along streams
– flat, lobed body with little green “horns”
20.2 Classification of Plants
• Mosses belong to phylum Bryophyta.
– most common seedless nonvascular plants
– sphagnum moss commonly used by humans as “peat”
20.2 Classification of Plants
Club mosses and ferns are seedless vascular plants.
• A vascular system allows club mosses and ferns to grow
higher off the ground.
• Both need free-standing water for reproduction.
• Club mosses belong to phylum Lycophyta.
– not true mosses
– oldest living group
of vascular plants
20.2 Classification of Plants
• Ferns and their relatives belong to phylum Pterophyta.
frond
fiddlehead
– whisk ferns and horsetails are close relatives of ferns
– ferns have large leaves called fronds
20.2 Classification of Plants
Seed plants include cone-bearing plants and flowering
plants.
• Seed plants have several advantages over their seedless
ancestors.
– can reproduce without free-standing water, via
pollination
– pollination
occurs when
pollen meets
female plant
parts
– seeds
nourish and
protect plant
embryo
– seeds allow plants to disperse to new places
20.2 Classification of Plants
• Gymnosperms do not have seeds enclosed in fruit.
– most gymnosperms are cone-bearing and evergreen.
– the cone is reproductive structure of most
gymnosperms.
– pollen is produced
in male cones.
– eggs are produced
in female cones.
– seeds develop on
scales of female
cones.
20.2 Classification of Plants
• Cycads are gymnosperms in phylum Cycadophyta.
– look like palm trees with large cones
– grow in tropical areas
20.2 Classification of Plants
• Ginkgos are gymnosperms in phylum Ginkgophyta.
– only one species alive today, Ginkgo biloba
– grown in gardens and used in urban landscaping
20.2 Classification of Plants
• Conifers are gymnosperms in phylum Coniferophyta.
– most common
gymnosperms alive
today
– includes pines, spruce,
cedar, fir, and juniper
20.2 Classification of Plants
• Angiosperms have seeds enclosed in some type of fruit.
– A flower is the reproductive structure of angiosperms.
– A fruit is a mature ovary of a flower.
• Angiosperms, or flowering plants, belong in phylum
Anthophyta.
20.2 Classification of Plants
KEY CONCEPT
The largest phylum in the plant kingdom is the
flowering plants.
20.2 Classification of Plants
Flowering plants have unique adaptations that allow them
to dominate in today’s world.
• Flowers allow for efficient pollination.
– animals feed on pollen or nectar
– pollen is spread from plant to plant in process
20.2 Classification of Plants
• Fruit allows for efficient seed dispersal.
– Fruit is flower’s ripened ovary
– Surrounds and protects seed(s)
– Many forms, each function in seed dispersal
20.2 Classification of Plants
Botanists classify flowering plants into two groups based
on seed type.
• A cotyledon is an embryonic “seed leaf.”
• Monocots have a single seed leaf.
– leaf veins usually parallel
– flower parts usually in multiples of 3
– bundles of vascular tissue scattered in stem
20.2 Classification of Plants
• Dicots have two seed leaves.
– leaf veins usually netlike
– flower parts usually in multiples of 4 or 5
– bundles of vascular tissue in rings in stem
20.2 Classification of Plants
Flowering plants are also categorized by stem type and
lifespan.
• Stem type can be woody or herbaceous.
– Wood is a fibrous
material made up of
dead cells.
– Wood has high
concentrations of
lignin and cellulose.
– Woody stems
are stiff.
Oak
20.2 Classification of Plants
Flowering plants are also categorized by stem type and
lifespan.
• Stem type can be woody or herbaceous.
– Wood is a fibrous
material made up of
dead cells.
– Wood has high
concentrations of
lignin and cellulose.
– Woody stems
are stiff.
– Herbaceous plants do not
produce wood.
Iris
20.2 Classification of Plants
• There are three types of plant life spans.
– Annuals mature from seed,
flower, and die in one year.
Wheat
20.2 Classification of Plants
• There are three types of plant life spans.
– Annuals mature from seed,
flower, and die in one year.
– Biennials take two years to
compete life cycle.
Foxglove
20.2 Classification of Plants
• There are three types of plant life spans.
– Annuals mature from seed, flower, and die in one year.
– Biennials take two years to compete life cycle.
– Perennials live more than two years.
Big bluestem