BIOA02H3 Lecture Notes - Lecture 1: Azolla, Eukaryote, Lycopodiophyta

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6 Feb 2016
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TREE OF LIFE PLANTS
Basal Tree of Life
All species of life are grouped into three domains
oBacteria
oArchaea
oEukarya
Includes Algae, Fungi, Plants and Animals
Bacteria evolved about 3600 million years ago where they led a solitary life until
more advanced life forms showed up
Green Algae evolved about 1200 million years ago
oWere able to fully photosynthesize, autotrophic
oWere ancestors of plants
Plants are grouped into
oBryophytes
Liverworts (6000)
Mosses (12000)
Hornworts (100)
Most advanced and the smallest branch of bryophytes
Closely related to primitive Lycophytes
oVascular plants
Lycophytes (1200)
Most basic vascular plants
Ferns (12000)
Seed plants
Gymnosperms (900)
Angiosperms (270000)
Alternation of Generations
oA haploid phase and a diploid phase
Bryophytes
Bryophytes are characterized by what characters they lack when compared to
vascular plants
oThey lack waxy cuticles which seal the leaf against water loss
Consequences
They lose water very fast
They lose & uptake water along whole surface
Can survive total desiccation
They are abundant in areas with a lot of rain
Ex. British Columbia vs Ontario
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oLack of a vascular system in bryophytes whereas in vascular plants the
system of xylem and phloem are used to transport water and sugar,
respectively
In bryophytes, the cells are not specialized for this transport system
so not an e:icient water/nutrient transport systems
Consequences
Bryophytes are very small because the lack of a vascular
system to strengthen the plant
Liverworts
oFlattened toward the ground, may produce protruding structures for sexual
reproduction
Mosses
oThey are generally small, di:erent in shape, color and size
Hornworts
oThe non-reproductive structure of the hornworts is similar to liverworts but
to reproduce the hornworts grow a horn like elevated structure
Life cycle of Bryophytes (Mosses)
oMale gametophyte (haploid) contains antheridium which are full of
spermatozoids (haploid)
oThe male gametes are released to the environment and moves toward the
female gametophyte (haploid) which contains an egg (haploid) within an
archegonium
oFor sexual reproduction to be possible in bryophytes, there needs to be water
since the spermatozoids are propelled by two =agella which requires a thin
water >lm to travel
oFertilization occurs to form a zygote (diploid) which mitotically grows into an
embryo then stretches out beyond its con>nes to form a sporophyte (seta and
spore capsule) (diploid)
oCells inside the sporophyte (diploid) goes through meiosis to produce spores
(haploid)
oSpores are released and if a good environment is found, the spores will
germinate and grow into a structure called the protonema (haploid) – very
thin branches which photosynthesize sugars and building blocks. Protonema
can be male-determining or female-determining
oIf enough sugar and building blocks are available, one of the protonema
(haploid) branches will develop a gametophyte (haploid)
oThe small gametophyte will grow into a full gametophyte to complete the
cycle
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