Transcript Chap22Bio112 - holyoke

Plant Diversity
Chapter 22
Miller & Levine Text
Biology 112
What Do You Already Know???
PLANTS
Introduction to Plants
Plants…
• Provide the base for food chains on
land
• Provide shade, shelter and oxygen
for all animals
Oldest fossil evidence of plants dates
from about 470 million years ago!
What is the name of the science of
studying plants??
Kingdom Plantae
• Multicellular
• Eukaryotic
• Carry out photosynthesis using
green pigments called chlorophyll
• Include trees, shrubs, grasses,
mosses and ferns
• Most are autotrophs
• Cell Walls made of cellulose
Plant Life Cycle
• Two alternating phases, a diploid
(2N) phase called the sporophyte
generation and a hapoid (N)
known as gametophyte generation
• These alternating phases are known
as “alternation of generations”
What do Plants Need?
1.
2.
3.
4.
Sunlight
Water & Minerals
Gas Exchange
Movement of Water and Nutrients
Early Plants
• For most of Earth’s history plants
did not exist. Life was concentrated
in oceans, lakes and
streams…Oxygen came from algae
and cyanobacteria
• The first plants evolved from an
organism much like the multicellular
green algae living today.
Overview of the Plant
Kingdom
Botanists divide the plant kingdom
into 4 groups based on three
important features:
1. Water-conducting tissues
2. Seeds
3. Flowers
Types of Plants
Cone-bearing plants
760 species
(gymnosperms)
Ferns & Relatives
11,000 species
Mosses & Relatives
15,600 species
235,000 Flowering
Plants (Angiosperms)
Bryophytes (Non-Vascular)
No Xylem or Phloem
• Confined to moist habitats b/c they
need water for sexual reproduction
• Commonly found in wetlands, rain
forests, and roadside ditches
• Generally less than 20cm tall
• 3 classes: mosses, liverworts, and
hornworts
Bryophytes
• Have leaflike, stemlike and rootlike
organs
• Have rhizoids (fine-like roots) that anchor
the plant
• Water and nutrients move from cell to cell
by diffusion
• Mosses are the most common and they
hold a lot of water – this sponge like
feature makes them useful in oil spills,
and potting soils
Seedless Vascular Plants
(Ferns & Relatives)
• Dominant land plant 300 million
years ago
• Most are now extinct
Seed Plants - Gymnosperms
• Represent all seed plants that DO NOT form
flowers (therefore do not have seeds enclosed
within a fruit)
• The most numerous and widespread are the
conifers
• Reproductive Adaptations and an improved
vascular system largely account for the success
of seed plants
• The most widely distributed and complex group
of plants on Earth
• 270 000 known seed plants
• Have separate male and female gametophytes,
as well as roots, stems and leaves.
Gymnosperms cont…
• Seed type is the main criterion for distinguishing
the two major seed-bearing groups;
gymnosperms and angiosperms
• Greek: sperma “seed”, gymnos “naked”, and
angeion “vessel”
• Gymnosperms produce unprotected or “naked”
seeds in conelike structures, and
• Angiosperms produce seeds that are enclosed
and protected inside the fruit, which is formed by
the flower.
• Seeds ensure the survival of seed plants by
resisting desiccation.
Conifers
• Cone bearing woody trees and shrubs
• Leaves are usually needlelike
• Most are evergreen (don’t drop their
leaves in the Autumn)
• Conifers DO shed their needles, just not
all at once – usually 2 to 4 years
• Grow in many different environments
• 600 species (pine, fir, spruce, cedar,
hemlock, sequoias
• Produce useful products, ie.
lumber/paper
Angiosperms – Flowering
Plants
• There are thousands of different kinds of
flowering plants
• They range from tiny pond-surface plants, which
are less than 1mm long to trees 100m tall.
• Angiosperms ALL produce seeds in reproductive
structures called flowers. Then, as the seeds
mature, the flower changes into a fruit.
• The name angiosperm means “covered seed”
• Mature seeds are scattered, or dispersed, along
with the fruit
• http://www.biology.ualberta.ca/facilities/multimed
ia/?Page=271
Monocots & Dicots
• Botanists are able to divide the 235,000
species of angiosperms into two large
groups based on the structure of their
seeds
• Inside the seeds of angiosperms are tiny
embryonic leaves called cotyledons.
The seeds of one group of angiosperms
have one cotyledon, called
monocotyledons or monocots.
• Other angiosperms have two cotyledons.
These are called dicotyledons or dicots
The veins of
monocot leaves
are parallel to each
other
The leaves of
dicots usually have
netlike veins
Monocot Examples
• Tulips, daffodils, irises, lilies, palm trees
Dicot Examples
• Buttercups, peas, roses, sunflowers,
maple trees, and dandelions
Grass?
• The leaf blade of grasses indicates
whether they are monocots or dicots
based on leaf veins.
• To which group to grasses belong?
• You are right if you said monocots!
Roots, Stems & Leaves
“Principal organs of seed plants”
Roots – Try This:
http://www.virted.org/Plants/RootsQuiz.html
• Absorbs water and dissolved
nutrients
• Anchors plants to ground
• Prevents erosion
• Protection from soil bacteria and
fungus
• Transports water & nutrients
• Holds plants upright against forces
such as wind and rain
Roots – Two main types:
Plants have taproots, fibrous roots or both
#1 Taproots - Characterized by having one main
root (the taproot) from which smaller branch
roots emerge.
• When a seed germinates, the first root to
emerge is the radicle, or primary root. In
conifers and most dicots, this radicle
develops into the taproot.
• Taproots can be modified for use in storage
(usually carbohydrates) such as those found in
sugar beet or carrot.
• Taproots are also important adaptations for
searching for water, as those long taproots
found in mesquite and poison ivy.
Taproot
#2. Fibrous Roots –
• Characterized by having a mass of
similarly sized roots.
• In this case the radicle from a
germinating seed is short lived and is
replaced by adventitious roots.
Adventitious roots are roots that form on
plant organs other than roots.
• Most monocots have fibrous root
systems.
• Some fibrous roots are used as storage;
for example sweet potatoes form on
fibrous roots.
• Plants with fibrous roots systems are
excellent for erosion control, because the
mass of roots cling to soil particles.
Fibrous Roots - A cabbage seedling with
white, fibrous roots snaking through the soil
Root Overview
STEMS
Stems have 3 important functions:
1. Produce leaves, branches, flowers
2. Hold leaves up to sunlight
3. Transport substances between
roots and leaves
Leaves – (see handout for
additional notes)
• The structure of a leaf is optimized
for absorbing light and carrying
out photosynthesis.