Download Plant Evolution - Cloudfront.net

Plant
Evolution
Plant Evolution
• Evolved from green algae
(450 mya)
– Evidence: Both have
chlorophyll, store
energy as starch, DNA
similarities
• Green algae ancestor
– Multicellular body
– Cells w/ channels to
communicate
– Reproduce w/ sperm &
egg
• Early plants
– Low growth
Okay, so we now know that plants
evolved from green algae…
What do we know about algae?
Yeah- mostly aquatic & unicellular,
some multicellular but low growth
(nothing really above water)
So, what sort of challenges do you
think land plants had to over come?
Land Adaptations
• Challenge: Retain Moisture
– Early plants grew near waters edge
• Solutions:
– Cuticle: waxy coating
– Stomata: pores to allow gas exchange
Land Adaptations
• Challenge: Transporting Resources
Vascular tissue consists of what’s
called xylem (ZY-LUM)and phloem
(FLO-M), that’s what the first picture
on the left shows. The picture on the
water)
right is of a cross section from a
plant stem. Those openings are
(ex: sugars)where that vascular tissue is.
– Solution: Vascular system- tissue to transport
nutrients
• Up from the roots (ex:
• Down from the leaves
– Allows taller growth
Land Adaptations
• Challenge: Growing upright
– Large plants need to support own weight
– Solution: Lignin- hardens cell wall; gives wood
strength
Land Adaptations
• Challenge:Reproduction on land
– Solutions:
– Pollen: carried by wind/animals
– Seeds: hard coat protects embryo
The first seed leaf (or leaves)
that sprouts is called a
cotyledon(s). Those that only
have 1 leaf are called
MONOcots, and those with 2 are
called Dicots. This also helps to
classify plants…we’ll discuss this
more later.
inside
Alternation of generations
• Sporophyte (diploid)
– Begins when
sperm fertilizes
egg (zygote)
– Diploid zygote
divides by mitosis
to create a mature
sporophyte
– Meiosis produces
haploid cells called
spores
– Haploid spores
released
Alternation of generations
• Gametophyte (haploid)
– Begins with spores
created by meiosis
– Spore grows into
gametophyte
• Male gametophyte
creates sperms
• Female gametophyte
creates eggs
– Sperm & egg create
diploid zygote
(process repeats)
You’ll see this again later…
Plant Ecology
• Mutualistic relationships
– Type of symbiosis where
both organisms benefit
– Ex: Plants (provides living
space)/Bacteria (create
nutrients)
– Ex: Plants (provide
food)/Insects (help
pollinate)
• Herbivore interactions
– Defense adaptations
– Spines, thorns,
chemicals,
What to do now??
You can start your homework if you’d
like (dice pgs. 617-618 & 665)
To do that (view the online textbook) you must
have already created an account on
classzone.com (you only need an account to
view the online text…not to play games, etc.)
If you want to create an account, please do!
The access code is 2631090-10.
Otherwise, you may work on anything
else…as long as you’re PRODUCTIVE and
not socializing!!! BE GOOD! 