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L 21.1 & 21.2 Introduction To Plants (21.1 Plant evolution and…
L 21.1 & 21.2
Introduction To Plants
21.1 Plant evolution and Adaptations
Plant evolution
Biologists describe plants as multicellular eukaryotes with tissues and organs that have specialized structures and functions.
multicellular land plants and present-day green algae share a common ancestor
common characteristics:
the same type of chlorophyll used in photosynthesis
cell division that includes the formation of a cell plate
similar genes for ribosomal RNA
cell walls composed of cellulose
food stored as starch
the same types of enzymes in cellular vesicles
Plant adaptations to land enviroment
Vascular tissue :specialized transport tissue.
vascular tissue enables faster movement of substances than by osmosis and diffusion, and over greater distances.Vascular tissues also provide structure and support.
Stomata: are openings in the outer cell layer of leaves and some stems
They are adaptations that enable the exchange of gases even with the presence of a cuticle on a plant.
Cuticles: fatty coating on the outer surface of their cells.
helps prevent the evaporation of water from the plant since it is a lipid and lipids are insoluble in water
Alternation of generations
gametophytes (haploid)(produces gametes), sporophytes (diploid)(produces spores (n))
Simpler plant --> 1n more dominant
complex plant --> 2n more dominant
Plant Classification
seedless vascular plants
lycophytes--club mosses
pterophytes —ferns and horsetails.
seeded vascular plants
ginkgophytes—ginkgoes
coniferophytes—pines and similar plants;
gnetophytes —joint firs
anthophytes—flowering plants.
cycadophytes —cycads or sago palms
Nonvascular plants
anthocerophytes-hornworts
hepaticophytes—liverworts
bryophytes—mosses;
21.2 Nonvascular Plants
Diversity of Nonvascular Plants
Division anthocerophyta
common name: hornworts (because of their hornlike sporophytes)
one large chloroplast in each cell of the gametophyte and sporophyte.
the spaces around cells are filled with mucilage, or slime, rather than air.
The cyanobacteria and hornwort exhibit mutualism.
Division Hepaticophyta
common name: liverworts (Because of their appearance and use as a medicine to treat liver ailments)
Liverworts tend to grow close to the ground and in areas where moisture is plentiful
osmosis and diffusion to transport nutrients
Liverworts
Thallose
a body that resembles a fleshy, lobed structure.
Leafy
have stems with flat, thin leaflike structures arranged in three rows
They have unicellular rhizoids unlike mosses who have multicellular rhizoids
Lack DNA sequences that most other land plants contain.
Division Byrophyta
common name : mosses
do not have true leaves, mosses have structures that are similar to leaves.
Mosses produce rootlike, multicellular rhizoids that anchor them to soil or another surface
Although mosses have some tissue that transports water and food, these plants do not have true vascular tissues.
osmosis and diffusion to transport nutrients
live in a variety of places but they prefer damp areas
Prepared by: Ghadah AlSudairy 11A
