Biodiversity (Plants) Flashcards
What did plants evolve from
Green algae
How many known plant species are there?
325,000 known plant species today; most live on land
What are the closest relatives of plants
Green algae (photosynthetic protists) called charophytes
Key traits of plants that also appear in some algae
- Plants and some algae are multicellular, eukaryotic, photosynthetic
autotrophs - Some algae, like plants, have cellulose in their cell walls and chloroplasts containing chlorophyll a and b
Sporopollenin
- a polymer that charophytes have a coating of which prevents zygotes from drying out
- found in plant spore walls
Why move to land?
- unfiltered sunlight
- more plentiful CO2,
- nutrient-rich soil
- Initially,morespace!
Why not move to land?
- scarcity of water
- lack of structural support against gravity
Four key traits appear in nearly all plants but are absent in the charophytes
- Alternation of generations
- Multicellular, Dependent Embryos
- Walled spores produced in sporangia
- Apical meristems
Alternation of generations
life cycles alternate between two generations of multicellular organisms: gametophytes and sporophytes
What does the multicellular haploid gametophyte produce
haploid gametes (sperm and eggs) by mitosis
Spores develop into
gametophytes
Fertilized eggs (zygotes) develop into
sporophytes
The diploid embryo is retained and protected within the tissue of
the female gametophyte
Nutrients are transferred from parent to embryo through
placental transfer cells
Plants are called embryophytes because
of the dependency of the embryo on the parent
The sporophyte produces spores in multicellular organs called
sporangia
Spore walls contain sporopollenin, which makes them
resistant to harsh environments
Apical meristems
Localized regions of cell division at the tips of roots and shoots
These cells divide continuously, enabling
elongation of roots and shoots for better resource acquisition
cuticle
a waxy covering of the epidermis that
reduces water loss
stomata
pores that facilitate gas exchange between the outside air and internal plant tissues
Early plants lacked …… making absorption of nutrients from the soil challenging
true roots (and leaves)
420 million-year-old fossils suggest that symbiotic associations with fungi (mycorrhizae), may have
helped plants without roots to colonize land
When did microorganisms colonize land
3.2 billion years ago