LEC 1 – Tree of Life
5 main plant groups
• Basal tree of life
• Bryophytes mosses
• Angiosperms – flowering plants
All life is organized into bacteria, archaea, eukaryotes (visible to naked eye, multi cellular organisms,
fungi + animals)
Green algae= photosynthetic & multi cellular, direct ancestor of plants
Bryophytes = typically three groups, mosses, liverworts, and hornworts. But mosses are made up
with two independently derived branches (it’s two diff groups of mosses even though one is
Seed plants are angiosperms & gymnosperms
The bulk of bryophytes is made of the mosses
A lot of diversity of the entire group of plants can be found in angiosperms (flowering plants)
Bryophytes – don’t know when originated, cannot fossilize well but close to algae
Very different in comparison to vascular plants (fern, flowering plant)
1. They lack the cuticle layer
Bryophyte has a simpler organization of leaf than vascular plant
All plants except for bryophytes have a transparent waxy film (on both the upper and lower layer)
which seals upper and lower surface against water loss Vascular plant has better protection against water loss
Bryophytes lose and uptake water easily from both upper and lower side of leaf
Sun light hitting bryophytes, it heats up the water and water evaporates = bryophyte doesn’t have
To deal with this, since there is no upper cuticle, it uptakes the water when available, they can
take up water even through their leaves (different from plants in which we water the roots so they
can uptake it, bryophytes do not need this).
Bryophytes survive losing water! – Even though the sunlight evaporates all of their water, they
How? They are adaptive to the water loss. When water evaporates the plant shuts down and goes
into thermal or dry hibernation and as soon as there is water it picks up its metabolism and starts
Bryophytes only grow if there is water. They’re found in very moist environments, [creeks, under
trees (where moist and sun hits shortly)]
• The forest that has more rain, there is more bryophytes because there is a lot of moisture and
they can grow, but dry air prevents them from growing, prevents the surface (trees, soil) from
2. They do not have vascular tissues
Vascular plants have vascular tissues connecting tips of roots to tips of branches and leaves.
xylem (transport water to roots upward motion) phloem (transport sugars produced in green
tissue into rest of plant – downward)
vascular tissue Is very sturdy (especially xylem) plants with this tissue use it as a back bone to
stay upright and grow tall (example: tomato, even though it’s not woody, vascular tissue helps it
Bryophytes don’t have vascular system (no specialized island in vascular plant) with the tissue so
there is no specialized system for nutrient and water transport as there is in vascular plants.[In
bryophytes there is epidermis and hypoepidermis, one type of cell+ cortex]
In bryophytes the transport is slow and passive compared to the vascular plants where it is tubing
system w/ specialized activity.
B/c they cannot efficiently transport water and nutrients (sugars) fast across plant bodies, they
have to stay small and rely on passive transport. They have no backbone due to lack of vascular
tissue, this is why mosses are small look like green carpets
Imperfect adaption for terrestrial life:
B/c of the lack of cuticle and vascular tissue in bryophytes, they are not very adaptive to life in
terrestrial habitats or out of the water. They cannot move into drier conditions because they lose water and because they cannot
transport nutrients well they need to be in moist conditions.
Liverworts: marchanta polymorphia
Archegonia – female
Mosses: largest group of bryophytes, come on diff colours, grow in bogs, can be pink. But most are found
in moist forest on ground
Hornworts: unique morphology, similar to liverworts, grow flat in plains but grow a horn like structure
giving them their name
Generalized alternation of generation
Plant Life Cycle
1. Gametophyte [haploid n] goes through mitosis, forming female and male gametes
2. After fertilization [diploid 2n] and zygote is made. Zygote continues growing through mitosis
into an embryo
3. embryo continues growing through mitosis into a saprophyte
4. specialized plant organs on saprophyte under go meiosis to make haploid spores
5. Haploid spores germinate through mitosis and will grow into gametophytes
Red= haploid generation
Blue = diploid generation
Life cycle of bryophytes: mosses
Both female and male start as gametophytes. Male gametophyte = antheridium a sausage like
structure filled with hundreds and thousands of spermatozoids (haploid). Spermatozoids have two
mobile tales which help them swim towards egg cell. Female gametophyte archegonium (egg
Fertilization in bryophytes is totally dependent on water because the spermatozoids compared to
animal sperm is not an active swimmer, it needs at least a thin film of water coating so they can
wiggle their way and enter in the archegonium for fertilization to happen, resulting in zygote
• Zygote out grows the case of the arcehegonium, resulting in diploid generation growing on
top of haploid generation.
• The developing sporophyte is on a stalk and there is a developing spore capsule.
• Gametophytic generation supports the growing saprophytic generation (already fertilized
Archegoinum develops a stem (seta) and is supporting a spore capsule (2n)) • Sporophyte cell in spore capsule go through meiosis turning diploid into haploid spores
• Once haploid spores are ripe and ready to release capsules breaks open. They get carried by
wind and they fall on ground. If there is enough water the pores start germinating and grow
into a threadlike tissue system – protonema
Protonema: thin hair like structure, start photosynthesizing right away and put the excess
sugars into developing buds which then grow into gametophytes. It is a green, haploid, once
it’s produced enough sugars it shuttles it to a growing bud which develops into a young
gametophyte (likely all haploid)
• B/c embryo has parent’s genetic material, half of these developing cells are female
determining and the other half is male determining. Half grow into femal
gametophyte and half into male.
Gametophyte is photosynthetic, and the sporophytic generating (seta) is not green doesn’t feed itself,
capsule is kind of green (short lived) sporophytic generation is dependent of haploid gametophytics
generation for survival, sugar is shuttled from n to 2n, after meioses spores start germinating so the
protonema is green and photosynthesizes. Haploid = green, sporophyte is depended on n generation.
Two mobile life cycle phases
• Spermatozoid actively propel through two mobile flagella, water dependent dispersal.
• Spores produced in sporophytic generation are adapted to wind dispersal. Wind spores travel
further, spores are the ones produce thing like volcanic islands, long distant dispersal make
the spores adaptive and help them survive longer perdios in air without dying in contrast
water dependent dispersal happens from male gametophyte through water film to the female
Gametophyitc generation is more long lived and sporophytics generation grows on top of the
Lycophytes similar life cycle to fern
• Look like liver mosses, flattened bodied, with the structure ending in sporanges, similar
looking to hornworts
• Can conquer life outside water, because they do have cuticle
• stomata, and vascular tissue so they can more effectively transport water (take up with roots)
allowing them to grow taller, and use vascular bundle as a backbone
• Have waxy cuticle to seal stem to prevent loss of water
• Have stomata to exchange air for photosynthesis w/ stomata construction in lycophyte is
similar to young angiosperms today
• Lycophyte vascular tissues has small dark xylem, and phloem Club mosses 400 species
Quillworts 150 live exclusively in water
Spike mosses 700
Whisk ferns 2 species
Horsetails 15 species
True ferns 12000 species
True Ferns – azolla smallest fern, grows on top surface of water with roots submerged in water
Life cycle of fern
Mature fern = sporophyte, on the lower side of leaves ferns produce sori, this is where fern produces its
• Sorus is a container that contains spores, once they are ready to be released container opens
and spores are carried by the wind.
• Sori undergo meiosis (dip to hap), spores get released and in ground with water germinate
and grow into a prothallium (gametophytic hap)
Prothallium: small, heart shaped, has roots to acquire water and nutrients. Produced antheridia on lower
side (male gamete) and produce archegonia on the upper side (female gamete)
• Antheridia produces spermatozoid, entwined flagella but can still propel through water
• Archaegonium has one single haploid egg cell. Spermatozoid swims towards egg cell,
fertilization occurs and diploid embryo starts to develop.
• Diploid embryo develops into sporophyte that is taking shape of fern, will mature into fern
(mature sporophyte) [sporophyte grows on prothallium]
Gametophyte and saprophyte is green and photosynthetic
Mobility: spores are wind depended, long distance dispersal, spermatozoid move themselves over short
The two generations are food wise “independent”
• Spores vs gametophyte life cycle = gametophyte stays for only a few weeks, diploid –
sporophytic generation is dominant than the haploid gamerophytic
• Ferns better equipped with sand drought bcause of cuticle, but prthallium does not have
cuticle so it it can dry out in sun light so it needs to germinate in shady conditions. ALSO spermatozoid does need water film to propel, fern as a whole are dependent of water so they
are more abundant in tropics and not deserts.
Conifers 700900 species
Gingko 1 species
Ephedra 35 desert species
• Have cones & are reproduced by cones
• In mature and fertilized cone, there are two female seeds, scaled pointing outwards and male
cones: scale towards sides, have pollen which has air bags that makes them easy to be carried by
• Gymnosperms – ‘naked seed’ the seed that grow on top of the scales are naked, the seeds lay on
the scales without protection, no extra layer around seed.
Have adapted well to drier conditions, some have a wing that allows seed to be moved away
from mother plant.
The seed is equivalent to the spore so they are more drought resistant and long lived in
comparison to spores.
Proper vascular plant, have 2 vascular bundles in center for water and nutrient transport
Cuticle has stomata (like lycophyte) for air exchange/ photosynthesis
Wood Sturdy, allows conifers to stand tall.
Angiosperms – the flowering plants
First evidence in Jurassic time period and became dominant in the cretaceous period.
• Flowers make angiosperms successful. Flowers figure out the needs for pollinators.
Example: beetle pollinator are white b/c beetles cannot see colour but since they have a
good sense of smell they smell well and + landing platform for beetles.
Life cycle for seed plants
• Mature apple tree (sporophyte, dip) some cells in flowers undergo meioses to form hap. Male
gametophytes – pollen, eggs hidden in ovary = female gametophyte.
Anther – male reproductive organ
Stigma female reproductive organ [style connected with stigma connected with ovary which creates hap.
• Pollen gets released from anthers and pollen lands on correct stigma. • Pollen germinates and grows through style to ovary and fertilization makes diploid embryo
which grows into apple.
• The protective tissue around seeds of angiosperms sets them apart from gymnosperms (no
Angiosperms ‘covered seeds’ get free from parents plant, and start germinating that will grow
into mature sporophytes.
Tree of life key evolutionary inventions
1. Cuticle stomata – liverworts, mosses, hornworts, lycophytes
2. Vascular system – ferns, lycophtes
3. Seeds flowering plants
6. Double fertilization
Interpretation of life cycle
• In brycophytes. gametophytic is dominating over sporophytics
• In fern, sporophytics in dominant.
• In seed plants, gametophytics is so short and contained in spore that it is hardly ever seen,
dominant is sporophytic generation.
Feeding dependence of life cycle who photosynthesises?
• In bryophyte: gametophyte feeds sporophyte
• In fern: both generation are photosynthetic
• In seed plants, sporophyte feeds gametophyte
• Both bryco and lyco there is spermatozoid but in lyco/fern they are entwined, but they can
propel through water similarly + spores are wind dispersed
• in gymnosperm; pollen = wind seed= wind or animal
• Angiosperm: wind/animal pollen long distance. Seeds= wind/animal long distance
Plant cells and plant tissues
Growth: difference b/w plants and animals is indeterminate vs. determinate growth.
• Plants have indeterminate growth, start out with seedling and continue growing every year,
whereas animals have determinate growth. If plants grow they need undifferentiated cells
(meristematic cells) and they divide into differentiated cells and more undifferentiated cells and
these continue dividing into indeterminate growth in plants
• Animals start out with undifferentiated cells and divide into differentiated cells which go into
determinate growth. In plants, totipotent cell [meristematic cells] (grow/different time) give rise to
meristematic cells and differentiated cells. This continues and results in an indeterminate
growth in plants, as long as plants contain their organs (meristem growth tips) they can
continue to grow.
In animal, totipotent cell [stem cells] differentiated cells only give rise to undifferentiated
• Factors limiting growth in plants: wind, herbivores that feed off plant, activity of sun that heats
up tissue at the very top of plant (ex. tree) it becomes harder to absorb the water, and soil can
have missing nutrients so there is a limit in tree growth. We can predict what a plant can look like
but not animals
Primary meristems: shoot (where plants grows up) and root meristems as seedling continues growing
organs secondary meristems become important
Secondary meristems: many different ones, at different locations
Shoot apical meristem: Located at tip of plant surrounded by developing embryonic leaves that are
produced by the action of meristems that give it protection, which is really important for roots. SAM is
located above the tip of the root, it produces root cap cells, SAM is throw away material used to allow the
root to grow in the soil. As root grows and pushes itself through gravel SAM cells get peeled off so the
abrasive action does not touch the root meristematic cells.
Differentiated plant cells
Differentiated plant cells make plant tissues
Simple plant tissue = one cell type
Complex plant tissue = more than one plant type
Simple plant tissues:
Made up of parenchyma cells (most commonly found cell type in any plant body). They are alive cells at
maturity (have all active cell organelles) Have a thin cell wall. Are the least specialized (can be used for
many diff purposes) Typical size is a block shape. Found in potatoes, apples, and some peanuts.
Have 3 main uses b/c they are least specialized
• Space fillers
• Except for thin layer epidermis and vascular bundles, everything is parenchyma cells
• Called chlorenchyma b/c the cells have many chloroplasts to use for photosynthesis.
• Parenchyma cells closest to the sun are arranged in a way to get as much as light as possible, in
lower portion of leaf they are more looser so the space between these cells can be used for gas exchange. Loose network allows sufficient transfer of CO2 into stomata and release oxygen
through loose cells out of leaf.
• Water, nutrients (root, leaves, seeds, fruits)
• Are alive and have all typical cells that maintain plant cells
• Are elongated
• The cells walls are thickened, especially in corners the cell wall is fixed/thickened
• Give flexible support to young stems (2 yrs)
• Protect and strengthen vascular bundles
Surrounds vascular bundles to give structural support to tubing system of vascular bundles. Also surround
vascular bundles in stems. Stems are supported by bundles of collenchymas cells.
• Are dead at maturity, b/c the cell walls have been growing so vigorously towards the cell so
all the interior organelles get squeezed and crushed and die.
• Cell wall made largely out of cellulose supported with lignin
• Sclereids: short and bulky
• Fibers: thin and long
Sclereids: short and bulky but can be branched. They occur as a single or aggregated in groups. + Hard
seed core (in a pear and in nuts because they want to keep nut safe inside [build strong shell around it]
Fibers: Extracted from flax plants, occur in bundles with thick cell wall and smaller cells in comparison to
surrounding sclerenchyma cells. Cell bundles occur at back of stem.
Complex plant tissues:
• More than one cell type. Specialized for protection, exchange uptake transport, support, and
• Cell protection, made up of epidermis cells– more than one cell type involved
• Covered with cuticle • In order for gas exchange, epidermis complex tissue have stoma with 2 guard cells for air
exchange and loss of water
• Glands, for protection and hairs
• Hairs used for protection against too much sun, hairs located on roots help take up water and
• Typically present on non woody plants or herbs, and short lived.
Present along the whole plant surface
Epidermis and water loss (+ defense)
• Waxy layer cuticle: fatty substance (cutin) The thicker the cuticle, the stronger the protection
against water loss. Thicker = lower permeability and protection again bacteria & other pests.
[grapes protection so retain water to be juicy]
Epidermal Glands: Hemp (cannabis sativa)
- Gland heads are filled with oils that contains THC, oil is used for protection (is toxic to
insects) natural function of these plants is protection against herbivores. The female
flowers has a lot of these glands, hemp distribution is similar to animals – male and
female. Female flowers are way more treasurable/important in contrast to male plants. If
insect eats female flower plant can’t reproduce even though