Transcript Botany

Botany
Evolution and Classification of
Plants
Why Plants are Great
• Plants were the first multicellular organisms to
colonise the land.
• Plants are Producers that is they get their
energy from sunlight. All animals rely on plants
directly or indirectly.
• Almost all food chains except those around
hydrothermal vents have plants at the start.
• Fossil fuels are made from dead plants…okay
maybe not so great now, but our civilisation
depends on it.
• Plants produce oxygen, stop soil from eroding,
stop the earth becoming to saline, provide
homes for animals, provide food and shelter,
they are the source of most medicines…the
list goes on.
What is a plant?
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Plants photosynthesise
Plants have cell walls made of cellulose.
Plants are eukaryotic.
Plants are autotrophic.
Autotrophic, what the hell does that
mean?
• Being Autotrophic means that an
organism makes its own organic
molecules.
• This is as opposed to heterotrophic
organisms that take there organic
molecules for the environment.
• Plants are photoautotrophic, meaning they
make their organic molecules using the
energy from sunlight.
Plant Evolution
• Over time plants have evolved and become
more and more well adapted to land so that they
have conquered most land habitats.
• Plants that are still alive today represent the
evolutionary path that plants took (though we
must remember that these modern plants are all
well adapted to their preferred habitats – they
aren’t “un-evolved”).
Three Major Phyla
• Algae
– Simple plants
• Bryophytes
– Non Vascular Plants
• Tracheophytes
– Vascular plants
Algae
• Are simple single or multicelled plants.
• They are completely dependant on
water to survive and reproduce.
• Have no true tissues.
• May form colonies of cells as in seaweed.
Bryophytes (Mosses and Liverworts)
• Are dependant on water for reproduction but
can survive on land without drying out (as long
as they have a fairly moist environment).
• Alternate between sexual and asexual
reproduction.
• Gametophytes produce sperm and eggs and
are Haploid, meaning they have one set of
chromosomes.
• Sporophytes are Diploid meaning they have a
set of chromosomes from both their parents.
• No true stems, leaves or roots. They known as
non-vascular plants
Tracheophytes (vascular plants)
• These plants have true Roots, shoots and
leaves and a well developed vascular
system.
• Includes:
– Ferns (plants that reproduce with spores)
– Gymnosperms (reproduce sexually using
seeds but have no flowers) (Conifers)
– Angiosperms (flowering plants)
Plant evolution
Questions
• Page 9 Q 1.12
• Page 10 Q 1.13
• Page 11 Q 1.14
• Page 12 Q 1.15
Tracheophytes: subdivisions
• Ferns
• Seed plants:
–Gymnosperms
• Conifers
• Gingkos
• Cycads
–Angiosperms
• Monocots
• Dicots
Questions
• What do cyanobacteria have to do with
plants? What is this process called?
• Why are plants important?
• Why do bryophytes need water to
reproduce?
• Why are bryophytes so small?
Levels of Classification
• Kingdom
– Plant
• Phylum
– Algae
– Bryophyta
– Tracheophyta
• Sub Phylum: Seed Plants (Spermatophyta)
• Class
– Ferns (Filicopsida)
The following 3 classes are sometimes all classed as
Gymnosperms but the classification is no longer used
officially.
• Cycads (Cycadopsida)
• Ginko (Ginkopsida)
• Conifers (Coniferopsida)
– Flowering plants (Angiospermae)
• Subclasses Monocotyledons and Dicotyledons
Levels of Classification continued
• The following categories contain fewer
plants and there are lots of them.
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Order
Family
Genus
Species