Exam 3 Flashcards
What was the first group of plants that had branched sporophytes?
Rhyniophytes
What are some reasons sporophytes became dominant in land plants?
In order to compete for sunlight, plants needed to become taller. At the time that sporophytes became dominant, reproduction still required water for the sperm to be transferred to the egg. This happens more easily at ground level. So the gametophytes remained small and on the ground while the sporophytes grew tall to get more light. Another contributing factor is that sporophytes have 2 copies of each gene and are therefore protected from the effects of mutation.
What was the first group of land plants to have true stems? Which group of plants had the first true stems, roots, and leaves.
The Rhyniophytes had true stems.
The lycophytes have true stems, roots, and leaves.
Name three Lycophytes
Lycopodium, Selaginella (spike moss), Isoetes (quillwort)
What is the big difference between Lycophyte and Bryophyte lifecycles?
the Lycophyte generations are independent and the Sporophyte is dominant.
Selaginella, the spike moss, is a lycophyte. It is heterosporous and has a special structure that produces true roots. What is the name of that structure?
rhizophore
In Selaginella what are the two types of spores called?
Megaspores and microspores.
In Selaginella, where does fertilization take place?
In the archegonia in the gametophyte.
Name three types of plants in the Monilophytes.
True ferns, horsetails and whisk ferns
Psilotum is a whisk fern and is in the Monilophytes. It is homosporous and has.
true stems but not true leaves or true roots
Equisitum, horsetails, are Sphenophytes and belong to the Monilophytes. They are homosporous and have
true stems but not true leaves or roots
The largest group of Monilophytes is
true ferns
Characteristics for true ferns
-have a leptosporangium
-The spores germinate and grow into gametophytes
-the leaves have stomata
The word gymnosperm means
“naked seed”
-the seeds are borne on scales and fruit is not
present.
Gymnosperms are ______ dominant?
sporophyte
- the gametophyte is not free living so we say the
gametophyte is dependent.
Two major evolutionary advances that appear in the gymnosperms are
pollen and seeds
Conifers, Cycads, Gingkos, and Gnetophytes are all
gymnosperms, Trachiophytes (have true vascular tissue), and all have secondary growth (wood).
What is pollen?
The male gametophyte protected by the spore wall.
When did the earliest seed plants appear? Were humans around then?
-Around 400 million years ago.
-No, the first humans appeared around 200,000 years ago.
What is a seed?
It is a plant embryo, with some stored food, enclosed in a seed coat.
-The stored food in gymnosperms is primarily female gametophyte tissue.
-In angiosperms it is endosperm.
-In some angiosperms the endosperm is abundant (as in maize) in others the endosperm is almost completely used up by the time the seed matures (as in beans) and the stored food is present in the cotyledons.
What are the advantages to seeds?
-Think about the differences between young sporophytes of
ferns vs. pines. The young sporophytes in gymnosperms can be dormant, can be dispersed by wind or animals, and are protected. Those are advantages of producing seeds.
So,
- Young sporophytes no longer need to grow and photosynthesize immediately (it can go dormant.)
-The sporophyte can be dispersed by wind or animal vectors.
-Sporophyte is protected.
-The sporophytes of ferns are not dormant, they are not dispersed, they grow directly out of the gametophyte.
-Disadvantages: very costly to make
Ovule
this is the megasporangium (2n) surrounded by the integument (2n) before the ovule becomes a seed. All of this is diploid, the sporophyte produces a cell that undergoes meiosis.
Integument
protective covering of the ovule, sporophyte tissue that becomes the seed coat
Nucellus
The megasporangium is called a nucellus in seed plants, it is 2n sporophyte tissue and produces the megasporocyte that undergoes meiosis.
Micropyle
The integument has an opening at one end called the micropyle that allows the pollen tube entry.
Megaspore
The megaspore is the first product of meiosis (so it is haploid) and it gives rise to the megagametophyte (n) (egg sac).
Gymnosperms are _______ and spores are called
-heterosporous
spores are called:
-microspore
-megaspore
Pollen is the ______ in gymnosperms
-immature male gametophyte
-When the pollen lands on a female cone it grows and matures before it produces sperm cells.
In gymnosperms the megaspore develops into
a multicellular female gametophyte.
Gingko
Dioecious (male and female plants), Large trees with fan shaped leaves. The male
gametophytes produce large flagellated sperm. Ovules are borne on stalks rather than cones.
Cycads
Dioecious, long-lived, compound leaves, seeds dispersed by birds, flagellate sperm,
pollination can take up to 10 years, some pollinated by insects.
Conifers
Most have woody seed cones (do not be confused about conifers with fleshy seeds
such as yews - they are not fruit), wind pollination, it takes about two years for conifers to
produce seeds, so a long life cycle compared to angiosperms (or some earlier plants such as
mosses and ferns).
Gnetophytes
-three genera: Ephedra, Gnetum, and Welwitschia.
○ Vessel elements in xylem
○ Ovules surrounded by fleshy layer
○ Similarities to flowering plants
Fascicles
clusters of needles (2-5 in pines, except for pinyon pine which has single needles).
lifecycle of Pine
the main features: dominant sporophyte generation, dependent gametophytes, the megasporangium (nucellus) produces a megasporocyte that undergoes meiosis, one megaspore survives to become the female gametophyte, development of seeds from fertilized ovules, pollen delivers the male gametophyte to the ovule, in the seed, the embryo is surrounded by female gamotophyte (1n) tissue, etc.
Name some deciduous gymnosperms
larches, dawn redwood, and bald cypress.
Angiosperm means
-seed within a vessel
-angiosperms are flowering plants
Important developments in Angiosperms:
-ovules enclosed in ovaries (the ovary forms the fruit),
-pollen enclosed in stamen,
-double fertilization,
-further reduced male and female gametophytes increases the speed of egg development and pollination.
Advances that appear in angiosperms:
-improved vascular system with xylem vessels and sieve tube elements and companion cells (compared to only sieve cells in gymnosperms).
-Flowers appear in angiosperms; they aid in pollination and protect developing seeds.
-Fruit appears and it is important for dispersal of seeds
In angiosperms the reduced male gametophyte is
-pollen with two or three cells and the female gametophyte has seven cells and eight nuclei and is called the egg sac.
There are also strategies in angiosperms to reduce self pollination such as
dioecious plants, timing of pollen/stigma maturity (dichogamy), position of anther and stigma, and self-incompatibility (molecular).
The classic basal angiosperm is
-Amborella which has flowers but lacks vessel elements.
-Other basal angiosperms are water lilies and star anise.
Core angiosperms are
magnolids, monocots, and eudicots.
Eudicots are defined using a single characteristic:
tricolpate pollen all eudicots have it and no other plants have it.
Alismatales are
basal monocots.
○ Sepals and petals are distinct and in whorls. Nectar is present, pollination is done by bees and flies.
Characteristics of monocots:
-single cotyledon,
-leaves have parallel veins,
-flower parts in threes,
-stems have scattered vascular bundles,
-absence of secondary growth,
-adventitious fibrous root system
The monocot flower is surrounded by
bracts: a pair of glumes, a lemma and a palea
Features of eudicots:
-net venation,
-flower parts in fours or fives,
-two cotyledons,
-stem vascular bundles in rings.
Buttercup is a basal eudicot with the following characteristics:
- lobed leaves, superior ovary position (above the petals), seeds with small embryos. So those are basal eudicot characteristics.
The three largest groups of eudicots are
Rosids, Caryophylids, and Asterids.
Angiosperm reproductive strategies. Self pollination vs. cross pollination.
Selfing is good for pioneer species and it is efficient but cross pollination is important for recombining traits to generate variation and diversity.
Complete flowers
Flowers with all four sets of floral parts are complete flowers:
they have sepals, petals, stamen, pistil
Incomplete flowers
Missing at least one set of floral parts:
sepals, petals, stamen, pistil
Perfect Flowers
Flowers with male and female parts
Staminate flowers
incomplete, Male (only) flowers
Pistillate flowers
incomplete, Female (only) flowers
In angiosperms, Male gametophyte production occurs in
the anther, in the pollen sac
In angiosperms, in the mature male gametophyte the
generative cell divides into
two sperm.
Pollen is produced in
the stamen
pollination (in angiosperms):
transfer of pollen to the stigma
fertilization:
fusion of gamete nuclei, in angiosperms the egg gets fertilized and so does the central cell, there are two female gametes, the egg and the central cell.
The ovule develops into
the seed
the ovary develops into
the fruit
The seed coat is
maternal sporophyte tissue.
The fruit wall is called the
pericarp
-There are potentially 3 layers, the exocarp (skin), the mesocarp (flesh) and the endocarp which might be hard or tough.
Name two accessory fruits:
strawberry and pineapple.
Population
more than one individual of the same species
Community
all of the populations together in one place (plants, fungi, animals, protists and prokaryotes)
Ecosystem
the community along with the physical, non-living environment
habitat
the set of conditions in which an organism completes its life cycle
operational habitat
is the subset of conditions that affect the organism.
Habitat components:
abiotic are non-living components such as temperature, moisture, latitude (day length), disturbances, and biotic are all living components.
What are the two main types of soils in Minnesota and under
what vegetation did they form ?
alfisols and mollisols
-alfisols from forests and mollisols from grassland
What are very old soils called?
Ultisols, oxisols, paleosols.
Pioneer plants
change the soil and alter habitat so other species move in and out
○ They secrete acids that weather the soil.
○ Dead plants become substrates for soil organisms. This contributes organic mattermto the soil and that increases water holding capacity.
○ Roots penetrate the rock and expand cracks to break the rock.
○ Soil organic matter is the fraction of the soil that consists of plants, microbial, or animal tissue in various stages of breakdown.
Amensalism
-one sided negative relationships:
○ Example: an animal stepping on a plant.
Limiting factors
-applies to all aspects of plant interactions with its habitat.
○ Any factor in an environment can be limiting:
water, temperature, soil conditions, etc.
Local distribution:
- random, clumped, or uniform.
○ Random: not controlled by obvious factors.
○ Clumped: seeds fall near the parent, seed dispersal results in clumped deposition.
○ Uniform: even spacing not common in nature.
Denitrification:
returning nitrogen to the atmosphere in the form of N2
Nitrogen mineralization:
converting organic forms of N such as amino acids to the inorganic form NH4+
Nitrogen immobilization:
the opposite: converting NH4+ -> organic N
Nitrogen fixation:
atmospheric N2 to NH4+
mechanisms for N2 fixation:
-Biological (bacteria and cyanobacteria),
-Industrial (Haber-Bosch process, lightning, photochemical reactions in the atmosphere)
How old are soils in Canada and Alaska?
Much of the soil in Canada and Alaska was scraped off during ice age 8,000 years ago.
-Only relatively young soils exist there.
Allelopathy
plants release chemicals that inhibit other plants.
NO3- is toxic to animals
Causes Methemoglobinemia: NO3- –> NO2- in the liver. NO2- binds to hemoglobin. Fe2+ in hemoglogin oxidixed to Fe3+ , and in this form, it does not bind O2.
Concentration of carbon dioxide in atmosphere
~420 ppm
CRISPR/Cas9 is method to
do targeted gene editing and possibly a way to generate genetic changes in plants without a GMO label.
Two ways to generate a transgenic plant are
using the gene gun (biolistic transformation) and
via Agrobacterium.
the common characteristics of domesticated crops:
increased reproductive investment, increased fruit or seed size, uniform ripening, no seed dormancy, uniform germination, loss of seed dispersal mechanisms (hairs, burrs etc), non-shattering seed, non-dehiscent fruit, annual life cycle.
What are characteristics of green revolution plants?
these are generally semi dwarf varieties.
that only prokaryotic organisms (bacteria and cyanobacteria) can fix nitrogen and the enzyme they use to do that is
nitrogenase
The disease triangle indicates that plant disease can occur when
the pathogen can overcome the plant’s defenses, the host is susceptible and the weather is favorable for disease.
Dioecious means
there are separate male and female sporophytes
Glumes, lemma and palea are all flower parts from
monocots
In angiosperms, just prior to fertilization, the pollen tube cell fuses with and disrupts
a synergid
The pollen tube is attracted to the egg sac by peptides released by:
synergids
Arbuscules are produced by:
Glomeromycota
