Evolution of land plants Flashcards
When did colonization of land by plants happen
500 mya
Plants
multicellular, photosynthetic (photoautotrophic) eukaryotes
Plant cell walls are made of
cellulose
Plants contain chlorophyll _ and _
a and b
Plants store photosynthetic sugars in
plastids
Plants have life cycles with
alternation of generation
Closest living relative of land plants
charophytes (freshwater green algae)
Key traits plants share with charophytes
rings of cellulose synthesizing proteins, homologous structures of flagellated sperm, and phragmoplast formation during cell division (mitosis)
Phragmoplast formation during
cell division helps
construct a cell wall plate that fuses with the original cell wall, separating the two daughter cells
Kingdom Plantae is defined by clade ____
embryophytes (plants with embryos)
Moving onto land provided:
decreased competition, increased photosynthesis, atmosphere full of CO2, mineral-rich soils
Challenges to living on land
scarcity of water, lack of structural support to support upright growth
Adaptations enabling the colonization of land
sporopollenin, adaptations to conserve water, lignified vascular support tissue for internal transport, functional compartmentalization in terrestrial plants
Sporopollenin
complex, highly cross-linked polymer composed of C, H, and O that are resistant to degradation by enzymes and inorganic chemicals. It is a polymer secreted in the zygote cell wall and protect them from desiccation, UV light, stress
Sporopollenin is found in
cell walls of spores and pollen of plants
Adaptations of water conservation
waxy cuticle (reduces desiccation and protects from microbes) and stomata (allows for gas/water exchange between air and leaf)
Xylem cells
carry water and minerals up from roots which are strengthened by lignin
Phloem cells
distribute organic products
Lignified vascular tissue provides
rigidity supporting vertical growth and water transport that allows plants to grow in dry environments
roots functions
search for water & minerals underground
shoots functions
Search for light and gases aboveground
Alternation of generations evolved in
land plants by the addition of
a diploid
sporophyte generation
placental transfer cells
Nutrients are transferred from parent to embryo using these cells
A multicellular embryo is retained in
the tissues of the female gametophyte
sporangia
organs in the sporophyte that produce spores
Sporocytes undergo _____ to generate haploid spores
meiosis
sporopollenin
a spore wall component that makes them resistant to harsh environments, esp. desiccation resistant.
Multicellular gametangia
plant gametophytes produced gametes by mitosis within multicellular organs
______ do not have gametangia, but still produce gametes
flowering plants (angiosperms)
archegonia
female gametangia that produce eggs and are the site of fertilization
antheridia
male gametangia that produce and release sperm
Apical meristems
are localized
regions of cell division at the tips of
shoots and roots
Specialized epidermal cells for water conservation
cuticle and stomata
cuticle
waxy covering of epidermis that reduces water loss and protects from microbial attack.
stomata
cells that open/close to prevent water loss
Mycorrhizae
symbiotic associations between fungi and roots of land plants
Fossil evidence indicates that
plants were on land at least ___
470 mya
Land plants are grouped based on
presence or absence of vascular tissue
bryophytes
Nonvascular plants (non a monophyletic group)
three clades of vascular plants
lycophytes (mosses and relatives), monilophytes (ferns and relatives), and seed plants
Seedless vascular plants are _____
paraphyletic
Seed plants
embryos and nutrients surrounded by a protective coat
two clades of seed plants
gymnosperms (naked seed) and angiosperms (flowering plants)
