Lecture 5/6/7/8: Plants Flashcards
Plants can inhibit almost everywhere on land except…
some:
1. mountain tops
2. desert areas
3. polar regions
What is the key for other organisms to survive on earth? Why?
plants; they provide oxygen, food source, a habitat for some organisms
land plants evolved from what?
green algae
what type of green algae is the closest relative to plants?
charophytes
what are the 3 distinct traits that charophytes (type of green algae) that they share with plants?
- rings of proteins
- sperm structure
- phragmoplast
explain the ‘rings of proteins’ trait that charophytes and plants share:
- they both have protein rings in their plasma membranes that make cellulose in the cell wall
- circular, petal shaped arrays
explain the ‘sperm structure’ trait that charophytes and plants share:
shape and structure of the flagellated sperm is very similar
- looks like those big seashell conches
explain the ‘phragmoplast’ trait that charophytes and plants share:
structure that forms during cell division in both
what is phragmoplast?
a structure that forms during cell division
- helps organize the cell’s machinery to form a new cell wall (from cell plate) between the 2 daughter cells
what adaptations enabled the move to land?
- shallow water habitat
- survive dry periods
- layer of durable polymer called “sporopollenin”: prevents zygotes from drying out
what did the move to land provide for plants?
- bright sunlight
- carbon dioxide from air versus water
- soil had abundant of mineral nutrients
- initially less predators and pathogens
what were some challenges plants faced when they moved to land?
- relative scarcity of water
- lack of structural support against gravity
what adaptations enabled plants to overcome the challenges faced when they moved to land?
- Alternation of generations
- Multicellular, dependent embryos
- Walled spores produced in sporangia
- Multicellular gametangia
- Apical meristerms
what does ‘alternation of generations’ mean?
means that plants alternate between two different life stages or generations:
- Gametophyte (haploid stage)
- Sporophyte (diploid stage) DOMINANT
which stage is dominant for plants? Sporophyte or Gametophyte?
Sporophyte: the visible plant is diploid (the tip of the plant and stem, the ‘end’ of the process)
explain gametophyte stage for plants
prominent life stage where the entire plant body is haploid, where the plant produces gametes directly. (the roots- beginning of the process)
in general, how does the alternation of generations work?
- a male gametophyte and a female gametophyte produce gametes (sperm and eggs)
- they combine in fertilization to form a diploid plant, a sporophyte
- the sporophyte grows and produces spores through meiosis
- the spores germinate into a new gametophyte
repeat
multicellular plant embryos develop from what?
zygotes that are retained within tissues of the female parent
why are land plants also known as embryophytes?
because of the significant derived trait of the multicellular dependent embryo
what does the parent provide to the embryo for plants?
nutrients (sugars/amino acids)
plant spores are _____ reproductive cells that grow into ____________ by ______.
- haploid
- gametophytes
- mitosis
what makes the walls of spores very tough/resistant to harsh environments?
sporopollenin (a polymer)
what are the multicellular organs called that are found on the sporophyte and produce spores?
sporangia
what do the outer tissues of the sporangium do?
they protect the developing spores until they are ready to be released
what the difference between the female gametangium and male gametangium?
- FEMALE: produces a single cell in a vase shaped organ
- MALE: produce and release sperm into the environment
how does a zygote form and develop?
the sperm swims to the egg and they fuse within the archegonium (female gametangium), and then develops into an embryo
apical meristems differentiate (grow) into what 2 types of plant tissues?
- surface epidermis
- internal tissues
what are apical meristems?
special growth zones at the tips of roots and shoots that produce new cells
what are the two types of land plants?
- vascular
- nonvascular
whats the difference between vascular and non-vasc?
having a vascular system vs not having one
whats in vascular system?
specialized tissues;
- xylem (for transporting water and minerals)
- phloem (for transporting sugars and nutrients)
what do non vascular plants lack?
- vascular system, which in return lacks xylem and phloem
which plant grows taller, vasc or non-vasc? Why?
vasc, they have an efficient way to transport water and nutrients compared to non vasc
what are some examples of non-vasc plants?
mosses, liverworts, hornworts
what is the only plant with a life cycle in which gametophyte generation is dominant?
non vasc plants
what are non vasc plants informally known as?
bryophytes
what are the 3 phyla of bryophytes (non vasc)?
- mosses
- liverworts
- hornworts
in bryophytes, what is the largest and most conspicuous phase of the life cycle?
gametophytes are the largest
what are the filaments that are one cell thick on gametophyte called?
protonema
how do bryophyte spores germinate and grow into gametophytes?
mitosis
what is a protonema?
the early growth stage of bryophyte (like a baby moss)
- has a large surface area
- in turn helps it absorb water and minerals
- this is important because bryophytes live in moist environments
- in good conditions, protonema develops into gametophores
what are gametophores?
the structures that produce gametes (sperm and eggs).
- eventually becomes the leafy part of the moss
- only few cells thick, which allows all the cells to be close to water and dissolved minerals
- important because bryophytes don’t have complex systems to move water inside their bodies
what do most bryophytes lack?
non vasc, thus conducting tissues to distribute water and nutrients (transportation system)
what are bryophytes anchored by?
Rhizoids: tubular cells or filaments of cells
what’s the difference between rhizoids (non vasc) and roots (vasc)?
- rhizoids don’t play a crucial role in absorbing water/nutrients. just an anchor. not a true root as it lacks vascular tissues
- roots do play a big role in absorbing water/nutrients along with being an anchorage
what is the stage in the bryophyte life cycle that produces spores called?
bryophyte sporophyte
bryophyte sporophytes produce and release a huge number of _____
spores
is it true that photosynthesis is only temporary for sporophytes?
yes, only occurs in young sporophytes
the sporophyte is dependent on what part of the bryophyte for its entire life?
the maternal gametophyte (the green leafy part of the moss)
- it cannot survive on its own and stays attached to the gametophyte
why does the sporophyte stay on the gametophyte its whole life?
because the gametophyte provides essential resources like sugars, amino acids, minerals and water
what group of plants has the smallest and simplest sporophytes of all modern plant groups?
bryophytes
what are the 3 main parts of moss sporophytes?
- foot
- seta
- sporangium (capsule)
what is the ‘foot’ of the moss and its function?
it is the base of the sporophyte that anchors it to the parent gametophyte.
- absorbs water and nutrients from the parent gametophyte
what is the ‘seta’ of the moss and its function?
the elongated stalk that connects the foot to the capsule
- carries the absorbed nutrients and water from the foot to the capsule
what is the ‘sporangium/capsule’ of the moss and its function?
the top part where spores are produced
- the main reproductive part of the moss sporophyte
what is the sporangium/capsule protected by?
it is covered by a protective layer called the calyptra.
- comes from the gametophyte tissue
- layer falls off when the capsule is ready to release spores
what part of the bryophyte is specialized for gradual spore release?
the upper part of the capsule: the peristome
which type of bryophyte has the simplest sporophytes?
liverworts
which types of bryophyte sporophytes are larger and more complex?
moss and hornwort
what do the sporophytes of mosses and hornworts have that’s kind of like vascular plants?
epidermal stomata
what does hornwort resemble?
blades of grass, but have a cuticle
what does liverwort resemble?
kinda like a dog tongue
where can bryophytes habitat?
anywhere
which type of moss is abundant and widespread?
sphagnum (brown, loose looking)
what are wet regions dominated by sphagnum/peat moss also known as?
peat bogs
how do peatlands play an important role as carbon reservoirs?
they stabilize atmospheric carbon dioxide levels
what has sphagnum been used for in the past?
- diapers
- natural antiseptic material for wounds
what is sphagnum used for today?
- soil conditioner
- for packing plants’ roots
is moss vascular or non vascular?
non vasc- doesn’t have specialized tissues
how many clades are found within the vascular plants?
3
whats the main difference between the clades of vascular plants?
seeded vs. seedless (club mosses and ferns)
what were the main plants on land for the first 100 million years?
non-vasc plants (like mosses)
why were these early vascular plants (like ferns) key during the Carboniferous period?
b/c they provide insight on how plants evolved before seed plants (like trees and flowers) came along
quickly explain “Carboniferous period”
SHORTEN: Carboniferous - carbon in the form of coal was formed from the plants of that era
MORE EXPLANATION: really long time ago when Earth had huge swampy forests full of tall fern-like plants (grew tall from abundance of carbon dioxide and warm/wet climate). When these plants died they got buried and eventually turned into coal over millions of years.
where are vasc plants most commonly found today and why?
damp/moist environments: they need water so that their sperm can swim to reach the eggs and reproduce
what are the 5 main traits that modern vasc plants have?
- life cycle with dominant sporophytes
- transport systems (xylem and phloem)
- roots
- leafs
- sporophylls/spore variations (like pincones)
which generation is the dominant stage for vasc plants?
sporophyte generation
for vasc plants, the gametophytes are what?
tiny plants that grow on or just below the soil surface
what does xylem conduct?
conducts most of the water and minerals
what does phloem conduct?
conducts/distributes sugars, amino acids, and other organic products
what did vascular tissues enable for evolution?
- evolution of roots
- grow to greater heights
explain what roots are quickly
organs that anchor vascular plants and enable them to absorb water and nutrients from soil
what are leaves?
organs that increase the surface area of vasc plant
- allows them to capture more solar energy for photosynthesis
- classified as microphylls/megaphylls
whats the difference between homosporous and heterosporous plants?
HOMO: one type of spore that develops into a bisexual gametophyte (can produce both sperm and eggs). most seedless plants
HETERO: two types of spores-
1. Microspores = develop into male gametophytes (sperm)
2. Megaspores =develop into female gametophytes (eggs).
Most seeded plants, some seedless
whats the significance of seedless vascular plants?
- big impact on CO2: since these plants developed better systems that allowed them to photosynthesize more efficiently, this also meant they were able to take in way more CO2 from the air. this lowered CO2 levels up to 5 times.
- global cooling: with the dropped CO2 levels, the Earth’s climate cooled down
- plant material turned into thick peat layers, and then turned into coal
what was the single most important culture change in the history of humanity? why?
agriculture; made the transition from hunter-gathered societies to permanent settlements
what adaptations helped seed plants become successful?
- seeds
- smaller gametophytes
- pollen
- ovules
which type of vascular plants have tiny gametophytes that are still visible to the naked eye? (seed of seedless)
seedless vasc plants
are the gametophytes of seeded plants visible to the naked eye?
no- microscopicly small. they develop inside the sporangia
the gametophytes of ____ plants obtain nutrients from their parents, whereas the free-living gametophytes of _______ vasc plants must fend for themselves.
- seeded
- seedless
seed plants are unique in retaining their…
megaspores within the parent sporophyte
whats an ovule?
small structure found in seed plants that develops into a seed after fertilization
think ovule = ovaries
in angiosperms, where is the ovule?
it is enclosed in the ovary
in gymnosperms, where is the ovule?
it is exposed on the surface of cones before developing into seeds
what’s an integument?
it is the protective outerlayer of an ovule in seed plants
- protects the developing egg cell inside
- develops into the tough outer shell of a seed
what do microspores (male gametophytes) develop into?
pollen grains
how is pollen spread?
by wind or animals
the process of moving pollen to where the ovule is located is called ______
pollination
what happens once the pollen reaches the ovule?
it starts to grow a pollen tube, which allows the sperm to travel to the female gametophyte and fertilize
whats the difference between fertilization for bryophytes (seedless) and seed plants?
- bryophytes needed water for their sperm to travel
- seed plants rely on a pollen tube that directly places the egg inside the ovule without water
the ovules and seed of gymnosperms (aka ________) develop on the surface of modified leaves that usually form cones
naked seeds
think guys are naked in hockey gym
ovules and seed of _________ develop in enclosed chambers called _____
angiosperms; ovaries
whats the most familiar gymnosperms?
the confiers (cone-bearing trees)
- pines, fir, redwood, spruces, cedars
where in the world do conifers dominate large forests?
northern hem
what does evergreen mean?
leaves year-round
what does deciduous mean?
leaves fall in autumn
what further reduces water loss in conifers?
- thick cuticle covering the leaves
- the placement of the stomata
why is the wood of conifers very strong?
xylem tissue (aids the structural support)
what was the first see plants recorded? gymno or angio
gymno
main diff between gymno and angio
- GYMNO: conifer
- ANGIO: flowering/fruiting plant
think gymbros are straight and angio are fruity
explain mesozoic era quick
age of gymnosperms, where dinos were supported by forests mostly made up of gymnosperms like conifers and cycads
what are the 3 key adaptations to terrestrial life in seed plants?
- increasing dominance of the sporophyte
- seed as a dispersal stage
- pollen for reproduction
what are the two types of cones for pines?
- small pollen cones for male gametophytes
- large ovulate cones for female gametophyte
how long does it take from the appearance of a young cone on a pine tree to the formation of mature seeds?
3 years
all angiosperms are placed in a single phylum- phylum _______.
Anthophyta
what is the key structure in angiosperms that evolved specifically for sexual reproduction?
the flower
flowers (angiosperms) use ____ to help with pollination, others rely on _____.
animals/insects; wind
what are the 4 layers of special leaves for a flower?
- Sepals: located at the base of the flower. sterile, meaning they don’t participate in reproduction
- Petals: brightly coloured to attract pollinators, sterile
- Stamens: the male reproductive organs. has 2 parts, anther (produces pollen) and filament (the stalk that holds up the anther)
- Carpels: the female reproductive organs. pollen lands on the stigma, travels down the style, and fertilizes the ovule in the ovary
_____ help disperse the seeds of angiosperms
fruits
what is a fruit?
mainly a mature ovary of a flower
whats the purpose of a fruit?
help protect seeds and ensure they have a better chance of growing into new plants
what happens to the fruit if the flower isn’t pollinated?
the fruit doesn’t develop
what are the 2 fruit types?
- fleshy fruits (soft, juicy fruit wall when they ripen): oranges/grapes
- Dry fruits (fruit wall becomes hard/dry when mature): beans/grains
what kind of fruit is staple for humans?
the dry, wind-dispersed fruits of grasses
how are fruits classified?
according to whether they develop from a single/multiple ovary(s) or from more than one flower
the formation of a phragmoplast in an important part of the life cycle of charophytes. What are phragmoplast?
microtubes that form between daughter nuclei of dividing cell
what are cotyledons?
the first leaves (or seed leaves) that develop from the embryo of a seed plant
- they store food that provides energy for the seedling until it can produce true leaves and start photosynthesizing on its own
