Evolution of land plants Flashcards
why are land plants important?
almost all life on earth is land plants
fundamentally changed the environment on earth
primary producers in terrestrial food web
domestication and cultivation of plants
what is the origin of land plants?
land plants started to grow on beaches to have access to large amount of water
can get nutrients from the water
downside can’t get enough sun light to photosynthesize
what is the common ancestor of land plants
likely charophytes (green algae, stonewort)
what kind of group are Charophyta?
paraphyletic group
what is paraphyletic group?
a group that doesn’t have all of its decedents
what is a monophyletic group?
a group that has all of its decedents
Why was dryness a challenge?
had no control over water content and were restricted to moist areas
water was essential for reproduction
what was the first adaptation to fight dryness?
the cuticle
evolved early on but still had some water loss
present in all bryophytes
what was the problem with the cuticle?
prevented carbon dioxide to be taken up
solution was pores
what was the second adaptation to fight dryness?
stomata
present in moss and hornworts
prevented water loss and opened when carbon dioxide is needed
selectively and actively open and close
what are characteristics of bryophytes?
no vascular tissues
no roots
gametophyte (haploid) phase dominant
what is the challenge with competition for light and gravity?
grow upwards to get more light for photosynthesis
competition for light, lead to selection for growth and leaves to increase photosynthetic ability
what is the solution for competition for light and gravity?
lignin
makes secondary cell wall stronger and more strong and rigid
water proof barrier
resistant to decay and attack by microbes
what are microphylls?
single unbranched strand of vascular
lycophytes
- club mosses and scale trees
what is a megaphyll?
multiple, branched strands of vascular tissues
evolved at least twice independently
pterophytes
- ferns, horsetails and whisk ferns
what’s the challenge pf spatial segregation and transportation of resources
minerals and most water is in the soil
light and carbon dioxide for photosynthesis above ground
where does primary growth happen?
the apical meristems at the root and shoot tips
what do roots and shoots provide?
they provide support for the plant and transportation of minerals, water and organic substances
what is mineral transportation?
short distances between cells
long distances between roots and shoot parts (xylem and phloem)
what is phloem?
vascular tissue which conducts sugars though the plant body
what is xylem?
vascular tissue which conducts water and dissolve minerals from soil to roots to shoots
what are mycorrhizia?
good at extracting nutrients from the soil and give to the plants
plants will give them sugars in return
what are hydroids?
like vascular system but for moss
independently evolved (convergent evolution)
functions the same and xylem and phloem
what are most seedless vascular plants?
homosporous
some are heterosporous
