Card Set Information
evolution of land plants
A megaspore is...?
a female spore
A microspore is...?
a male spore
Multicellular, photosynthetic eukaryotes that range in size from the duckweed to the giant coastal redwoods.
When did plants evolve? What evidence?
believed to have evolved from freshwater green algae over 500 million years old.
Contain chlorophylls a and b and various accessory pigments.
Store excess carbohydrates.
Green Algae ancestry. How is this known?
terrestrial plants arose from a green algal ancestor.
both have the same photosynthetic pigments (chlorophyll a and b)
some green algae have a cell wall made of cellulose
cells divide similarly
largest and most diverse group of algae
: found mostly in fresh waters and on land
Float in rivers, lakes, resevoirs, creeks
Can also live on rocks, trees, soil
Plants evolved from algae
algae cannot survive on land
plants adapted characteristics
Earliest known land plant...
nonvascular and similar to today's bryophytes
Probable alga ancestor
both have same pigments (chlorophyll a and b, carotenes, etc.)
both use starch to store photosynthetic products
both have cellulose in their wall
both have alternation of generations
both form a cell plate during cell division
Adaptations for plants to obtain enough water
plants evolved roots to anchor the plant
roots to absorb water and dissolved minerals
Adaptation to preventing water loss
plants evolved a cuticle- waxy layer
evolution of multicellular gametangia (sex organs)- helped protect gametes from drying out.
evolution of a resistant coat on spores that prevents drying out
Adaptations to getting enough energy
In land, plants obtained enough sunlight for photosyntsis
different strategies for obtaining light
-growing taller and taller above other plants- plants began to evolve support cells
-others had to adapt to lower light intensities
such as mosses
vascular (xylem and phloem)
ferns and fern allies
Photosynthetic (water) dilemma
Problems- plants need pores for gas exchange for photosynthesis, but open pores (stomata) allow water to leave (95% water taken is lost)
solution- stomata open during the day (for photosynthesis gas exchange) and close during the night (to allow platn to recover from water loss)
Affects of having multicellular organism
: roots better, protect gametes, grow tall to obtain sunshine
: getting water to all cells
Algae vs Plant Life Cycle
: water dependent life cycle.
: water independent life cycle in land plants. plants developed dry-resistant gametophytes (spores) or zygotes (seeds).