Transcript Plants - Smith College

Plants
C. Bustamante, M.Covington, M.
Santistevan, A. Urias, & R. White
Introduction
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1950’s classification
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two kingdoms: plants
and animals
Advancement of
Technologies = ability
to discern more
subtle, yet profound
differences in the
living world
New 5-kingdom
model evolved
Introduction continued…
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Based on the 5kingdom / 2superkingdom model
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plants belong to the
superkingdom Eukarya
and the kingdom
Plantae
(Some authors differ
about the definitions of
the largest taxons
placing Bacteria and
Archaea on an equal
footing with Eukarya)
Introduction continued…
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Distinction of plants from other organisms
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life cycles rather than by their capacity for
photosynthesis
few plants (beech drops, Epifagus,) are heterotrophs,
lost green pigment in the course of evolution and
derive their organic material from other organisms
majority are photosynthetic autotrophs, use solar
energy, atmospheric carbon dioxide, water, inorganic
materials to synthesize organic compounds
dominant contribution:
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food, fiber, coal, oil, wood and other forms of stored
energy that sustain the rest of the biota, maintain
oxygen in the atmosphere
Plant reproduction
has the
distinguishing
characteristic of
alternating
generations of
diploid (doublechromosome)
sporophytes and
haploid (singlechromosome)
gametophtyes,
illustrated here for
a fern.
Introduction continued…
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Some photosynthetic
organisms once classified as
plants due to color and
sedentary habit no longer
considered plants because
they lack embryos and other
criteria for plant classification
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Cyanobacteria (blue-green
algae),
green algae
lichens (fungi with bacteria or
protoctist symbionts
Introduction continued…
Differentiation
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Though cyanobacteria and plants utilize chlorophylls,
greenish pigments, that capture the energy of sunlight
And Cyaobacteria were architects of the earth's
atmosphere through aquatic and photosynthetic
characteristics,
it was the plants, which emerged to produce and
maintain land-based life on the earth
Introduction continued…
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All plants, algae, and
cyanobacteria that
photosynthesize
contain chlorophyll “a”
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There is also
chlorophyll "b", which
occurs only in "green
algae" and in the
plants
Introduction continued…
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To date there are some half-million species of
plants identified – new ones found each year.
Oldest fossils-430 million years old in the
Phanerozoic eon
Have aquatic ancestors
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appear to have evolved from only a small group of
green algae
Plant Evolution
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Prerequisites for survival
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sunlight for energy,
air for carbon dioxide,
crucial inorganic nutrients, and
water
Coping with life on the land
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Sunlight, air, and nutrients readily available
Need for water to support metabolism and
reproduction drives evolution
Plant Evolution continued…
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12 plant phyla divide into two major groups
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3 phyla of non-vascular plants (Bryata or, informally,
bryophytes) and
9 phyla of vascular plants (Tracheata or
tracheophytes)
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Bryata are most closely related to plant ancestors
among the green algae (Chlorophyta)
Non-Vascular Plants (Bryata)
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The three Bryata phyla are
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Hepatophyta (liverworts)
Anthocerophyta (horned worts)
Bryophyta (mosses)
Non-Vascular Plants (Bryata)
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Bryophytes differ from vascular plants lacking
vascular tissue
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plant body is typically a low-growing organism that
lacks differentiated leaves, stem, and roots
Absorb nutrients directly from the environment,
anchoring to soil, tree bark, and rock via rootlike
structures called rhizoids
in contrast to the vascular plants, the dominant
phase of the lifecycle is the gametophyte phase
Non-Vascular Plants (Bryata)
continued…
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Bryophyte sperm have undulipodia (flagellae)
that enable them to swim to the female
gametophyte, but require fresh water to bear
them to the egg
They may also exhibit asexual reproduction, by
fragmentation
Uses of Bryata
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moisture-holding capacity of soils, and
when dried, used as fuel
Vascular Plants (Tracheata)
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Non-seed-bearing (4 phyla)
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Seed-bearing (5 phyla)
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All reproduce by means of spores rather than seeds
“Naked” seeds (Gymnosperms; 4 phyla)
Seeds enclosed in the fruits of flowers (Angiosperms)
Contain lignified fluid-conducting vessels
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Two kinds of vascular cells
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Xylem carries water and minerals from the roots to the rest of
the plant
Phloem transports photsynthate to other tissues
Seedless Vascular Plants
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Four Phyla
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Lycophyta (club mosses)
Psilophyta (whisk ferns)
Seedless Vascular Plants continued…
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Four Phyla
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Sphenophyta (horsetails)
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Filicinophyta (ferns).
Seedless Vascular Plants continued…
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The earliest seedless vascular plants lacked
differentiation of tissues between root and shoot,
and between stem and leaf.
The evolution of these tissues enabled plants to
reach great sizes.
In all vascular plants, the sporophyte is the
dominant life-cycle phase.
Seedless Vascular Plants continued…
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Some uses include
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lubricants
fireworks
medicines
Some are edible for humans, but poisonous to
livestock.
Ferns provide food, thatch, tea, dyes, medicines,
and even pillow stuffing.
Gymnosperms (Naked seeds)
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A seed is a mature ovule enclosing an embryo
and stored food within a durable coat.
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Gymnosperms, like seedless plants, are
heterosporous.
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It provides enormous advantages in survival over
freely dispersed spores.
i.e., sharp differences between male microspores
(pollen grains) and female megaspores
They include 5 orders, 15 families, about 70
genera, and 730 species.
Gymnosperms (Naked seeds)
continued…
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Four gymnosperm phyla are
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Cycadophyta (cycads),
Ginkophyta (represented by the a single surviving
species Ginkgo biloba),
Coniferophyta (conifers), and
Gnetophyta (gnetophytes),
Gymnosperms (Naked seeds)
continued…
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Seed production evolved
by at least 360 million
years ago.
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extinct progymnosperms
produced seeds, but no
flowers or fruits
Cycad cones exhibit an early
(possibly the earliest) animal
pollination system, attracting
insects with odors and heat
Gymnosperms (Naked seeds)
continued…
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Cycads - palm-like, but
not true palms
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live in the tropics and
subtropics; are listed as
endangered species
uncooked seeds are toxic to
humans and livestock,
cooked seeds are edible
leaves are used as thatch
and dressing for wounds
Gymnosperms (Naked seeds)
continued…
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Ginkgo- leaf veins
that split into two
smaller veins
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edible;
leaf extracts have
found medicinal uses
Gymnosperms (Naked seeds)
continued…
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Confers — largest gymnosperms
Uses include
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lumber and other wood products
pulp,
resin products,
edible seeds, and
medicinal
Gymnosperms (Naked seeds)
continued…
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Gnetophytes – live in a wide variety of regions
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Namibian Desert,
North America,
Mediterrenean, and
Himalayas to Mongolia
Uses include:
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Medicinal, and
Limited as food
Angiosperms (flowering fruit bearing)
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Anthophyta – the most
abundant plants
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produce flowers, wherein
fertilized eggs become seeds
surrounded by nutrient-bearing
fruits
include plants as grasses (e.g.
corn, wheat, barley), lilies,
daffodils and palms
Flowers may be single or
clustered
reproductive elements of the
flower are the stamen and the
pistil
Angiosperms (flowering fruit bearing)
continued…
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Provide the basis for most human foods and the
source of most pharmaceuticals.
Plant Relationships
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Plants occur in many
ecosystems and adapt to
climate and precipitation,
elevation, and soil types.
Plant communities that
are found over large
areas are referred to as
biomes.
Plant Relationships continued…
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Plants provide (living)
structure to the ecosystem as
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And additional surface area
as
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cover soil (grass),
middle canopy (shrubs),
upper canopy (trees)
roots, leaves, stems, branches,
and trunks
Which it provide a means of
exchange for materials and
energy as well as habitat for
other organisms
Plant Relationships continued…
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Biodiversity - amount of different kinds of living
organisms in an ecosystem
Can also be described
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by the differences between individuals of the same
species (intraspecific diversity).
Studies show that stability of an ecosystem is
positively related to the diversity present.
Plant Relationships continued…
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Plants are producers in ecosystems.
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Autotrophs – produce their own food.
Derive energy from the sun
Convert atmospheric carbon into sugar
(photosynthesis).
Consumers get their energy from consuming
producers.
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Carbon is the basis of life on Earth and is largely made
available to the other kingdoms by the plants.
Plants provide carbon in the form of dead plant matter
(shed leaves, needles, stems, twigs, rotting trunks,
etc.) to the soil environment
Plant Relationships continued…
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Plant respiration produces oxygen!
Oxygen is central to the metabolism of the other
kingdoms, especially the animal and fungi
kingdoms.
Integral with the production of biomass, plants
require sugar to provide energy for growth,
defense, and reproduction.
Plant Relationships continued…
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Herbivory
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primary producers and
provide the basis for
secondary productivity
(herbivory or grazing)
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Energy relationship between
primary and secondary
producers may differ by an order
of magnitude (i.e., as little as
10% of the biomass consumed
becomes biomass for the
consumer).
Plants are central to the
survival of consumers by
the transfer of biomass
Plant Relationships continued…
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Herbivory continued…
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plants also provide nitrogen.
although the atmosphere is
largely composed of nitrogen
(79%), the gaseous phase of
nitrogen (N2) is not available to
living systems
nitrogen pathways are complex
and mediated by a plethora of
bacteria species.
Nitrogen, fixed by bacteria and
assimilated by plants is
available to other kingdoms by
grazing (animals) or
decomposition (bacteria and
fungi).
Nitrogen Cycle
Nitrogen Cycle
Water Cycle
Plant Relationships continued…
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Plant Communication
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Respond to light, gravity, nutrients, and touch
Signal via sight, smell, touch, and chemical signals
Plant Relationships continued…
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Disturbance and Succession – unable to move
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Disturbances can be any event that drastically alters
the structure and function of an ecosystem such as
fires, floods, landslides, or any other natural (or
unnatural) disaster.
Plants will begin to reestablish themselves in the
cleared area by a process of succession.
Plant Relationships continued…
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Co-evolution
wind, earth, fire, and water are central to the
survival of plants and other kingdoms
Many plant species would not be able to
continue without the relationships with other
organisms
bacteria and worms are central to maintenance
of fertile soils and process organic matter
Animals are important to seed germination and
dispersal
Mycorrhizal fungi connect roots of the plant
Human agriculture
Conclusion
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Plants are primary producers in terrestrial
ecosystems
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Convert abundant sunlight, carbon dioxide from the
atmosphere, plus water and minerals from the soil,
into energy-bearing food for organisms in all the
other kingdoms.
Plant Evolution continued…
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Vascular plants divide
further
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non-seed-bearing (4
phyla) and
seed-bearing (5 phyla),
with seed bearing
fossil record includes extinct
plant phyla Zosterophyllum
and Rhynia with the oldest
vascular plants, the
lycopods (club mosses)