Transcript 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)
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