Download Introduction to Plants Powerpoint

Chapter 28: Plant Evolution and
Classification
Section one: Overview of plants
Adapting to Land
• Nothing could live on land until 475 million
years ago.
– The Ozone layer developed, which offered
protection from UV rays
• 3 adaptations allowed plants to survive on
land:
– Preventing water loss
– Ability to reproduce without water
– Ability to absorb and transport nutrients
Preventing Water Loss
• Plants had to go from
having total exposure
to water to the
constant threat of
evaporation.
• Cuticle – a waxy covering
on a plants surface that
prevents water loss
See any
problems with
this?
Preventing Water Loss
• They needed
protection from
evaporation that
didn’t cut off their
supply of CO2
• Stomata – Small
openings in the surface
which allow the
exchange of CO2 and
Oxygen.
Cuticle
Stomata
Reproducing by Spores and Seeds
• Plants had to develop reproductive structures
that didn’t dry out.
• Spores - Haploid
reproductive cells
surrounded by a hard
outer wall – allowed for
wide dispersal of plants
• Seeds - An embryo
surrounded by a protective
coat. Some contained the
tissue endosperm which
nourished the developing
plant.
Absorbing and Transporting Materials
• Some plants have Vascular
• When plants lived in
Tissue – transports water and
water, they could
dissolved substances from one
absorb the materials
part of a plant to another. It
around them
also helps support the plant.
• Plants needed a way to
It’s made up of two parts
get the nutrients from
• Xylem – Carries water and
the ground up into
inorganic nutrients FROM the
their entire structure.
roots TO the stems and leaves
•Phloem – Carries organic
compounds (carbohydrates) and
some inorganic compounds to
wherever the plant needs them.
Classifying Plants
• There are 12 phyla of plants (used to be called
divisions)
• First they are separated based on if they are
Vascular or Non-Vascular
– Non-Vascular plants: No true vascular tissue,
roots, stems or leaves
– Vascular plants: Have vascular tissue, roots, stems
and leaves
Vascular Plants
• These can be further separated: Seedless vs.
Seed plants
– Seed plants can be even further divided:
Gymnosperms and Angiosperms
• Gymnosperms: Seeds are not enclosed into a fruit
• Angiosperms: (Flowering plants) Produce seeds that are
enclosed into a fruit
Alternation of Generations
• Plants have a life cycle with two phases:
• Sporophyte or diploid cycle:
Spores produced
• Gametophyte or haploid cycle:
Gametes (Egg and sperm) produced
• The plants will alternate between both cycles
http://www.youtube.com/watch?v=jcWYAnmm-QE
Alternation of Generations
• In Non-Vascular plants the gametophyte is the
dominant stage. (Like in the video)
• In Vascular plants, the sporophyte is the
dominant stage. (example: Oak Tree)
In seedless vascular plants
the gametophyte is usually
a separate small organism,
that is really different from
the sporophyte
In seed plants the gametophyte is
usually is a very small parasite of
the sporophyte. Example:
gametophytes of flowering plants
are microscopic parts of their
flowers that aren’t photosynthetic.