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Lecture

Bio lab 12 Feb 2 2010

by OC4

Department
Biology
Course Code
BIO120H1
Professor
Ingrid L.Stefanovic

Page:
of 4
Biolab 12
Early atomphere is rich in hydrogen, sulphur and nitrogen, until the evolution of photosynthetic
organisms that were capable to of:
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2. Releasing oxygen in the process
A protective layer ozone began to form to protecing the terrestrial life from the ultraviolet rays of the
sun.
Photosynthesis, through the release of oxygen into the atmosphere, created a more hospitable
environment.
Major groups: bryophytes t lack trie vascular tissues
Tracheophyte t have treu roots, stems and leaves as well as vasular tissues.
Both groups lifecycle consists of an alternation between a diploid sporophyte generation and a haploid
gametophyte generation.
Design of plant body compromise of 2 parts t requirement of photosynthesis (max surface area to
absorb light energy and carbon dioxide) and the requirement of reducing the evaporation of water (min
surface area)
Part of the Descendant species adapt to new habitate, result in two different species t divergent
evolution
Some unrelated groups evolved into similar afaptations t converggent evolution
Plant attract the pollinator t two catrgories of attractants; primary and secondary
Primary attractants t satisfy a physiological demand t eg. Feeding
Secondary attractant t used to draw the pollinators attention to thw presence of the primary attractant.
Both primary and secondary attractants must work together for pollinator to occur.
Evolution of flower and pollinator t ist generalists pollinator, flower small and simple t then, more
effective pollinator, flower evolve to attract pollinator t now, specilists pollinators, flowers adapt to
attract certain pollinators.
Evolution trends towards flower specialization include the reduction in the number of floral part , and a
change from radical to bi lateral symmetry.
Some vertabrates can be pollinators as well t birds, bats, rodents~
Bryophytes:
On eof the most diverse group of plants
Small simple plants
Commonly found in moist environments
Lacking true leaves, stems or roots
Must absorb water for water transport t the life cycle of bryophytes requires an external source of
water
Fertilization reaquies water so that sperms can swim to eggs
Characterized byL
Alternation of generation t haploid gametophyte is the dominant
Diploid sporophyte is short lived and is physically attached to and nutritionally dependent on the
gametophyte.
Sex organs develop at the tips of a gametophyte: the antheridium contaion motile spetm
Archegonium contains a single egg cell! When they both moistented -- they ruputre and release the
sperm and the egg t the sperm will swim to the archrgonium and fertilize the egg t grow a sporophyte
and will arrached to the gamtophyte until its spores have been dispersed t then it dies, it has a stalk and
a sporangium which containing the spores t the spores will grow into new game tophytes and the life
cycle is repeated
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Non-seed Tracheophytes:
Simple plants possess true leaves, roots and conducting tissue but do not produce seed
Leaves specialized for photosynthetic activity, the roots uptake the minerals and water and the
conducting tissue (xylem and phloem) for transporting water, minerals and carbohydrates
Name means ^plant with tracheids_vwhich are water-conducting elemtns of the xylem
Ferns are the most abundant group of non-seed trachrophytes t about 12000 species
But clubmosses and horsetails were dominant 350 million years ago t today, few survived species
Their life cycle contain an alernation of generations, although neither stage is dependent on others for
nutrition
In non-seed trachephytes the sporophyte is the dominant
The sperm must swim through the water to fertilize the egg in the archegonium t this limint non-seed
tracheophytes to regions of high moisture or periodic wetting
The young sporophytes growa roots and grow indenpently of the gameophyte
Seed plants:
It[s a very important development in yhe evolution of land plants because the seed plants are not
depenedent on the water for transferring a sperm t which allow the seed plant to colonize much drier
climates
The two groups:
Gymnosperms and angiosperms
The gametypoyte generation is extremely small and reduced
Pollen grains are male gametophytes
The process which the pollen grain is transported to the vicinity of the female gametophyte is referred
to as pollination
After fertilization a multicellular seed is produced t has a seed cose an embryp and food-storing tissue
to support the developing sporophyte. The seeds can remisn dormant for may years until develop.
Conifers, cycads and ginkgos are the examples that have naked seeds t the seeds are protected by a
flower or a fruit
Flowering plants:
The dominance of angiosperm over all other groups of land plants
Highly diverse group t 250000 species
The seeds are carried in a ovary and then they develop into a fruit
Main parts for a complete flower t sepals(protect the flowering buds), petals(attract the potential
pollinators), stamens (consisting of filament and anther, produce the pollen grains t male gameyophytes)
and carpels (consist of stigma style and ovary)
Two large groups of flowering plants:
Monocotyledons t have a single cotyledon
Dicoryledons t have two cotyledons
The cotyledons serve as absorptive organs that take up and digest the endosperm t mostly in monocots
Enlarge and becom photosynthetic when the seed germinates t mostly in dicots
Adaptation of desert environment:
Two strategies:
Drought avoidance:
Have brief periods of annual growth
During long dry periods t the plants drop their leaves and enter a state of ^suspended animation_, when
contact with water t alive again. Other plants survive drought as dormant seeds in the soil
Drought tolerance:
2 ways for the roots to behave t shallow and have subsurfaces twith lateral root growth
Or deep with very little lateral growth.
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Leaves:
Become as spines which help dissipate the heat and reduce the exposed surface area.
Or they can become succulent storage tissues
Stem can act as a succulent storage tissue as well
Bee pollination:
Bees like nectar and pollen
Bumblebees and honeybees are regarded as social bees
The worker bees will trapped the pollens while picking up the nectar
Bees have color-sensitive vision and a highly-developed olfactory sense t picky about flowers to visit
Bee-pollinated flowers are often blue, violet, or yellow, and have a fresh scent.
Butterfly pollination:
Pollinate flowers by brushing against the anthers and stigmas while they feed on nectar
Butterflies and flowers are good example for coevolution
Not really good sense at odor but can differentiatea wide of colors t include red
Often has tubular mouthparts in order to get in nectar
Lazy inactive fliers t stick in cluster of flowers instead flying around
Moth pollination:
Same order as butterflies
Nocturnal habits
Have very good sense about order t the flowers that attract them would emit very nice order during
night time
blossoms are often white, since moths are able to detect light colours in the dark.
fly pollination:
two kindsÖ
nectar and pollen feeders and carrion flies
nectar and pollen feeders: feed on nectar or pollen
short proboscis force them to feed on simple flowers -- with little odor and mostly blue yellow or white
brush against the flower[s well-exposed sexual organs and transfer pollen
carrion flies:
feed or lay their eggs on rotting flesh
flowers which mimic the sense will attract the flies t flowers aer dark brown or purple
sex organs hide inside the flowers cause the flies to be trapped and touch the sex organ therefore
pollinate the flowers
beetle pollination:
more common in the tropics than it is in the remperate zones
tropical flowers are always sitck together which is good for beetles because they are relatively poor
fliers
two groups:
a) Pollen feeders: interested in two types of flowers t those with single large flat or bowl-shaped
blossoms, and those that occur in aggregations t because they are poor fliers
Most flowers attract them by emit strong odor because thebeetles have strong sense about the
odor
The flowers have their sex organs exposed to the beetles because their poor flying ability
b) Carrion beetles
Search for decaying flesh to eat and in which lay their eggs
Blossoms mimic rotting flesh
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