Biology 1106 Exam 2
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What is a protist?
a eukaryote that is neither plant, nor animal, nor fungi
Are protists a kingdom?
formerly were but not any more becuase wed have to include fungi animals and plants as protists which are their own kingdoms . it puts all eukaryotes in one kingdom bc protists are so diverse and we cant do that
Are protists polyphyletic or monophyletic?
polyphyletic- members of this group have different ancestors
what is a plastid?
organ that allows photosynthesis (ex: chloroplast)
What are some structural and functional differences of protists?
- most unicellular, some multicellular
- most nutritionally diverse eukaryotes
- Reproduction- some exclusively asexual, some sexual and reproduce by meiosis
What does it mean that protists are the most nutritionally diverse?
they can be photoautotrophs, containing chloroplasts, heterotrophs and absorb organic molecules or ingest larger food particles, or mixotrophs which can survive by photosynthesis or heterotrophic nutrition
Are prokaryotes sexual or asexual?
are protists eukaryotic or prokaryotic?
What are some differences between eukaryotic and prokaryotic cells?
- eukaryotic mulitcellular and unicellular while prokaryotes just unicellular
- eukaryotes true nucleus while prokaryote naked dna
- eukaryote has organelles bounded by membrane, prokaryotes do not
What are mitochondria?
- power house of the cell
- the location of cellular energy production (produce cellular energy using chemical energy from sugars)
What are chloroplasts?
- powerhouse of plant cells
- produce sugars using light energy
What is the equation for photosynthesis?
Energy+ CO2 +H2O--->sugars + O2
What is the equation for metabolism?
sugars + O2 ---->CO2 + H2O + Energy
What is endosymbiosis?
- a process in which unicellular organisms engulf other cells which ultimately become organelles in the host cells
- there is now considerable evidence that much protist diversity has origins in endosymbiosis
What are 2 examples of endosymbiosis?
- Mitochondria used to be their own organisms and evolved by endosymbiosis of an aerobic prokaryote (anerobic eukaryote engulfs aerobic prokaryote= mitochondria that cant live independently)
- Plastids evolved by endosymbiosis of a photosynthetic cyanobacterium
Which of the following statements would NOT provide support for the endosymbiotic origin of mitochondria and chloroplasts?
A. The inner membranes of mitochondria and chloroplasts have enzymes and transport systems that are similar to those found in living prokaryotes
B. Mitochondria and chloroplasts have the cellular machinery (including ribosomes) that are needed to transcribe and translate their DNA into proteins
C. Many antibiotics function by targeting bacterial ribosomes. The ribosomes of mitochondria and chloroplasts are completely insensitive to antibiotics
D. Both organelles have a single circular DNA molecule
C. because this shows that these organelles are different than the prokaryotes not similar, (and doesnt matter if their similar to eachother since they were engulfed by different organisms) bc they were once their own organisms
(this multiple choice question has been scrambled)
All eukaryotes have mitochondria or remanents of these organelles but only some have chloroplatsts or plastids. based on this what is the most likely to be the correct sequence of these events, from earliest to most recent in the evolution of life on earth?
1. origin of mitochondria
2. origin of multicellular eukaryotes
3. origin of chloroplasts
4. origin of cyanobacteria
5. origin of fungal- plant symbioses
- bacteria were first organisms (so cyanobacteria)
- all bacteria have mitochondria so mitochondria
- some prokaryotes have chloroplasts so they must have come before eukaryotes
- multicellular have both so must be after both
- you need multicellular organisms for symbiosis
What did the world used to be like before protists and plants?
anaerobic. the world became increasingly aerobic when protists and plants contributed oxygen to environment
a heterotrophic eukaryote engulfs a cyanobacterium evolves into red and green algae and the green algae engulfs another organism. explain the endosymbiosis.
- the heterotrophic eukaryote engulfing a cyanobacterium first is primary endosymbiosis bc its the first one
- the green algae engulfing another organism is secondary endosymbiosis bc it is the second engulfing.
What are the 5 supergroups of eukaryotes?
What is excavata?
- a clade characterized by its cytoskeleton and modified mitochondria
- include euglenozoans
What are Euglenozoans?
- Type of excavates
- can be predatory heterotrophs, photosynthetic autotrophs, mixotrophs and parasites
- Two best studied types are Trypanosoma and Euglena
What are trypanosoma?
- a kinetoplastid that is associated with sleeping sickness and transmitted by the teetsie fly
- the euglenozoans of genus trypanosoma are parasites
- they are experts at evading immune system bc they can change their surface proteins
What are Euglena?
- a mixotroph commonly found in pond water
- in sunlight: autotrophic
- in no sunlight: heterotrophic (can engulf by phagocytosis)
What are kinetoplasitds?
- group that includes trypanosoma
- they have a single mitochondrion with an organized mass of DNA called a kinetoplast
What are chroalveolates?
- a clade that evidence suggests originated by a secondary endosymbiosis event
- ---> the proposed endosymbiont (thing ingested) is a red alga, but not all chromalveolates are photosynthetic
- clade includes alveolates and stramenopiles
Why is it possible that the endosymbiont is a red alga even though not all chormalveolates are photosythetic?
bc all could have been derived from a common ancestor that engulfed a red algae but may have lost it due to adaptation
What are 2 types of alveolates?
What is the organism of apicomplexans?
- plasmodium- a parasite that causes malaria
- it is common for apicomplexans to have a two host cell cycle
What is plasmodium
- a parasite that causes malaria
- they have a nonphotosynthetic plastd that is likely of the red algal origin
- plasmodium requires both mosquitoes and humans to complete its life cycle
Why is it hard to fight plasmodium and treat malaria?
- efforts ongoing to develop vaccines for it
- appx. 2 million people die of malaria every year
- plasmodium can change its surface proteins continually, allowing it to evade the immunes system making it hard for drugs to fight it
What is required for plasmodium to reproduce?
must be in the gut of its mosquito host for part of life cycle andbe in liver and blood of humans for the other part
Explain the lifecycle of plasmodium
- mosquito bite injects plasmodium in the bloodstream through saliva
- plasmodium infect liver cells and divide to become merozoites
- merozoites enter RBCs causing fever, chills
- merozoites become gametocytes which are picked up when another mosquito bites human
- gametes form and fertilization inside mosquito-->release of more sporozoites
What are ciliates?
- group of chromalveolates, named for their use of cilia to move and feed
- ex: paramecium
- have large macronuclei and small micronuclei
- a single cell that can move, feed, remove waste, and undergo sexual recombination
What do the micronuclei in ciliates do?
- they function during conjugation (a sexual process that produces genetic variation)
- in conjugation, genetic material is exchanged, but not necessarily gamete production)
What is conjugation?
separate from reproduction, which generally occurs by binary fission in cilliates (no new indivaduals are produced, but genetic material is exchanged in conjugation)
What are paramecium made up of?
- microtubules (protein very highly conserved)
- contractile vacuole (allows it to expell excess water and avoid bursting)
- micro and macro nuclei
- food vacuoles to help eliminate waste
How many nuclei can paramecium have throughout its life cycle?
anywhere from 2-5
What is the life cycle of paramecium?
- micronucleus undergoes meiosis
- two cells swap micronuclei
- cells seperate and each divides by mitosis (asexual)
Which is not a characteristic of cilliates?
a. they use cilia as locomotory structures or as feeding structures
b. they are relatively complex cells
c. they can exchange genetic material by mitosis
d. they maintain water balance through vacuoles
e. they have 2 or more nuclei
- c. because they exchange genetic material by conjugation not mitosis
- after exchange they divide by mitosis
- they are complex bc of vacuole types, organelles and complex structures
What is the supergroup Archaeplastida?
- group including red algae green algae and land plants
- red and green algae are the closest relatives of land plants
- over a billion years ago, a heterotrophic protist acquird a cyanobacterial endosymbiont
- the photsynthetic descendents of this ancient protist evolved into red and green algae
- land plants are descended from the green algae
What are some characteristics of red algae?
- most multicellular
- some red algae not photosynthetic so they lose their pigment
- red algae with non functioning plasmid gets nutrients because they are chemoheterotophs and eat other species of green algae
What are some characteristics of green algae?
- named for their grass green chloroplasts
- plants decended from the green algae
- live in diverse environments- fresh water, marine, terrestrial
- unicellular (chlamydomonas)
- more complex, evolved in 3 ways
What are the 3 ways that green algae evolved?
- single cells form colonies that function together (ex- volvox) (cyanobacteria can also live in colonies even though their not multicellular)
- multi-cellular bodies formed by cell division and differentiation (different cells have distinct roles in multicellular organisms [humans have differentiated cells])
- repeated rounds of nuclear division without cytoplasmic division
What is a thallus?
algal body that is plantlike but lacks true roots, stems or leaves
What does the supergroup unikonta include?
- protists that are closely related to fungi and animals
- this group includes 2 clades: amoebozoans and the opisthokonts
- it is unclear whether unikonts seperated from other eukaryotes relatively early or late
What are amoebozoans?
- amoeba that have lobe- or tube- shaped rather than threadlike pseudopodia
- they include entamoebas and slime molds
What are entamoebas?
- parasites (3rd example of parasite) of vertebrates and some invertebrates
- entamoeba histolytica causes amebic dysentery in humans (intestine infection)
What are cellular slime molds?
- form multicellular aggregates (collections) in which cells are separated by their membranes
- cells feed individually but can aggregate to form a fruiting body
- dictyostelium discodeum is an experimental model for studying the evolution of multicellularity
What is the life cycle of a slime mold?
- some cells inn fruiting body become spores
- solitary feeding stage- engulf bacteria
- when food is depleted, hundreds of amoeba congregate and form a slug like aggregate
- stalk cells dry up after supporting the fruiting body
In what do protists play key roles in?
- ecological relationships
- they are found in diverse aquatic environments and are key producers (by photosynthesis) providing a large percent of energy
Protists are all alike in that they are
Which taxon of eukaryotic organisms are thought to be directly ancestral to the plant kingdom?
e. green algae
Pair up characteristic with protist:
e. green algae
1. micronuclei involved in conjugation
2. multi and unicellular
4. multi and unicellular
- euglenozoans: mixotrophs (autotrophs and heterotrophs)
- ciliates: micronuclei involved in conjugation
- apicomplexans: parasites
- amoebozoans: have uni and multicellular
- green algae: have uni and multicellular
how many cells are most living things on earth composed of?
What are the three domains? which are the most closely related?
- Eukarya, Archaea and Bacteria
- two most closely related: Archae and Eukarya
What are some key adaptations of prokaryotes?
(bacteria and archaea)
- they thrive almost everywhere including places too acidic, salty, cold or hot for other organisms
- most are microscopic, but their numbers make up for it
- they have astonishing genetic diversity
What are the three main shapes of prokaryotes?
- cocci: spherical
- bacilli: rod shaped
- spirilli: spiral
- we can relate bacteria by the morphological species concept
What are the chromosomes of prokaryotes like
cytoplasm bound one circular chromosome tangled up in a supercoil
What is the structure of a prokaryote?
- made up of cell wall, fimbriae, sex pillus, capsule, internal organization, chromosome supercoil, and flagella
- all of these structures cause for evolutionary success of the prokaryote
What is the role of the cell wall in prokaryotes?
- maintain the cell shape
- provide physical protection allowing environment survival
- prevent cell from bursting in a hypotonic environment
- the shape is defined bythe rigid cell wall structure
What is a bacterial cell wall composed of?
- contain peptidoglycan
- peptidoglycan synthesis is targeted by antibiotics such as pennicillin which blocks bacteria frommaking cell walls and hypotonic environnments will kill them
What is peptidoglycan?
a network of sugar molecules linked by poly peptides (links of amino acids)
What are archael cell walls made of
- they have chains of carbohydrates but lack peptidoglycan
- no protein
What are cells like in hypotonic isotonic and hypertonic solutions?
- animal cell: lyses
- plant or prokaryotic cell: turgid (normal)
- animal cell: normal
- plant/prokaryotic: flaccid
- animal: shrivel
- p&p: plasmolyzed
What is the fimbriae?
- hair like appendages that allow prokaryotes to stick together or to the host
what is the capsule?
- halo shaped structure surrounding prokaryotes
- made up of polysaccharides or proteins
- can protect pathogenic bacteria from being recognized by the immune system by forming a meshwork around the cell wall so that antibodies cannot bind to and recognize it
What are the two types of cell walls?
- gram positive: 1 membrane peptidoglycan layer... traps crystal violet and stains purple
- gram negative: 2 membranes. one outer membrane and one peptidoglycan layer below that... does not trap crystal violet and stains red
What is taxis?
movement towards/ away from a stimulus
What is flagella
- flagella on a prokaryote is much different than eukaryotic flagela, they are analogous structures, arose independently
- help movement in taxis
Explain the internal and genomic organization of prokaryotes.
- they usually lack complex compartmentalization like a nucleus
- some have specialized membranes that preform metabolic functions.
- they can have respiratory membranes that act like amitochondria to utilize oxygen for respiration or thylakoid membranes used for photosynthesis
What is the dna of prokaryotes like?
- genes contained on the chromosome and plasmids
- prokaryotic genome has less dna than eukaryotc
- most of the genome is in circular chromosome but others in plasmid rings
What is binary fission?
asexual method where the chromosome is coppied, restricion cytokinesis and a result of 2 daughter cells
What adaptations make prokaryotes so diverse?
- if a prokaryote is in a very harsh environment (no nutrients) they can sort of hibernate for a while by activating signal proteins: instead of 2 identical daughter cells in reproduction, one will be a daughter cell and the other a spore with much more protection
- prokaryotes reproduce very quickly by binary fission and can divide every 1-3 hours
- many prokaryotes can form metabollically inactive endospores which can help in harsh conditions
What are the 3 main sources of genetic diversity in prokaryotes?
- rapid reproduction (every time they reproduce there is a chance of mutation)
- genetic recombination due to horizontal gene transfer
What is horizontal gene transfer?
bacteria can share DNA or take it up from environment; movement of genes from one organism to another between species
Why is evolution in prokaryotes rapid?
low mutation rate but they reproduce sofast that the small mutation rate adds up because there are so many of them and they actually end up having multiple mutations
what are the 3 ways that horizontal gene transfer can happen?
What is transformation
uptake of foreign DNA from surroundings
What is transduction?
- movement of DNA from one strain to another by bacteriophage viruses that infect bacteria
- can result in the formation of pathogenic bacteria
- picking up DNA from bacterial viruses
What is the process of transduction?
- phage injects its genetic material into host cell
- dna copied/packaged
- accidental packaging of host cell DNA into phage head
- phage with bacterial DNA infects a new host and the bacterial DNA is introduced into the recipient cells genome
What is an example of transduction?
- ecoli (harmless) trasducted into a harmful e coli bc of this
- k12 got the ability from the phage hosts aquire DNA from bacteriophages
What is conjugation
- the process where DNA is transferred between 2 bacterial cells
- sex pili allow cells to connect and pull together for DNA transfer
- DNA travels through the sex pillus (mating bridge formed) from one to another and recombines in the genome --> you need a plasmid called an f factor for this
What is the F factor
- a piece of dna required for the production of sex pilli
- can exist as a separate plasmid or as DNA within the bacterial chromosome
- plasmid has an F sequence
What are R plasmids?
- plasmids that carry genes for antibiotic resistance
- bacteria can pass antibiotic resistance from one to another
What are the ways prokaryotes can obtain energy
- only prokaryotes can survive by all of these
What are the possible prokaryote metabolisms?
- obilgate aerobes
- obligate anaerobes
- facltative anaerobes
What are obligate aerobes?
require o2 for cellular respiration
What are obligate anaerobes?
will die in the presence of o2. use fermentation or anaerobic respiration
What are facultative anaerobes?
can survive with o2 and do respiration or without and will do anaerobic respiration
What is metabolic cooperation between prokaryotic cells of the same species
- each cell is capable of photosynthesis and nitrogen fixation but the presence of o2 inhibits nfixation so cant do both at once
- some cells will go through nfixation and pass ammonia between cells
- other cells will do photosynthesis and pass sugars between cells
What is nitrogen fixation
- can take n2 gas from air and convert it to ammonia
- cells that do this are called heterocytes
Where does metabolic cooperation between diff prokaryotic species occur?
dental plaques- many diff species live together
What is unique about archaea?
some live in extreme environments: called extremophiles
What is an extremophile?
- 2 types: extreme halophiles and extreme thermophiles
- extreme halophiles: live in highly saline environments (ex: halobacterium)
- extreme thermophiles: live in very hot environments
Do archaea have peptidoglycan in cell walls?
- no, still have cell walls but only bacteria have peptidoglycan
- they do have a circular chromosome
What are cyanobacteria?
- photoautotrophs that generate O2
- plant chloroplasts likely evolved from cyanobacteria by endosymbiossi
- ecological role: they create a lot of the earths oxygen
What are chlamydias?
- these bacteria are parasites that live within animal cells
- chlamydia trachomatis causes blindness and nongonococcal urethritis by sexual transmission
Examples of gram pos bacteria?
- bacillus anthracis (anthrax)
- slostridium botulinum (botulism)
Where does a lot of the oceans nitrogen and oxygen come from?
archaea and certain bacteria working together
What role to prokaryotes play in chemical cycling?
- chemoheterotrophic prokaryotes function as decomposers, breaking down corpses dead vegetation and waste products
- nitrogen fixing prokaryotes add usable nitrogen to environment
- archaea in oceans perform key steps in nitrogen cycle
- prokaryotes can also immobilize or decrease the availability of nutrients
What is symbiosis?
- an ecological relationship in which 2 species live in close contact: a larger host and a smaller symbiont
- 3 types: mutualism, commensalism, and parasitism
What is mutualism? ex?
- both organisms bennefit
- esynthesis of vitamins by intestinal bacteria
What is commensalism? ex?
- one organism benefits, other unaffected
- ex: barnicles on whale
What is parasitism?ex?
- an organism called a parasite harms but does not kill host and benefits
- ticks and dogs
- parasites that cause disease are pathogens
How do pathogenic prokaryotes cause disease?
- by releasing exotoxins or endotoxins
- horizontal gene transfer can turn harmless bacteria into pathogens
What are exotoxins?
- cause disease even if the prokaryotes that produce them are not present. released from the cell
- ex cholera toxin
What is an endotoxin?
- released only when bacteria die and their cell wall breaks down releasing it
- ex salmonella typhi
What is bioremediation?
- the use of organisms to remove pollutants from environment
- prokaryotes principal agents
What was not a challenge for the survival of the first land plants?
predation- barley any animals
What is the most related to land plants?
charophytes (green algae) they have the most in common
What are the requirements for complex multicellularity?
- adhesion between cells (physically linked together)
- cellular and tissue differentiation (diff cells have diff functions in diff areas)- complications: only some contribute to reproduction and loss of certain ones can be lethal
- 3 dimentional organization!
- some cells not on surface dont have access to O2 and environmental signals
What is bulk transport?
- transporting nutrients to cells throughout the body
- waste can be taken out this way too
- had to happen for multicellularity to happen
How do large invertebrates survive without a circulatory system?
all cells that need o2 get it bc the body plan either all cells face surface bc of holes or all cells that need O2 on surface while anaerobic cells inside
What is the difference between adhesion in animal and plant cells?
- animal cells: transmembrane proteins called cadherins and integrins as well as others
- plants: polysaccharides called pectins
What are apical meristems?
- tissues where there is lots of rapid growth (many divisions)
- help plants explore new nutritional environments ex: grow higher more access to sunlight
- cells from the apical meristems differentiate into various tissues
What are the 4 main derived traits of land plants
- alternation of generations
- sporopollinin (walled spores)
- multicellular gametangia (archegonium and antheridium)
- apical meristems
What does the sporophyte produce?
- its 2n
- produces spores in organs called sporangia
- sporocytes undergo meiosis to generate haploid spores, which disperse upon maturation
- spore walls contain sporopollenin, which helps protect the spores from harsh conditions (allowed land plants to move farther from water)
Where does the sporophyte develop from?
What are multicellular cametangia
- gametes are produced by mitosis in haploid gametophytes within organs called gametangia
- female gametangia: archegonia produce eggs and non motile, site of fertilization
- male gametangia: antheridia, site of sperm production and release
Where does the sporophyte embryo develop?
Explain alternation of generations
- haploid generation that produces haploid gametes by MITOSIS
- fusion of the gametes gives rise to diploid sporophyte which produces haploid spores by meiosis
- diploid embryo is retained within tissue of the female gametophyte (archegonium)
- nutrients transferred to embryo through placental transfer cells
Why are land plants called embryophytes?
bc of the dependency of the embryo on the parent
What are some other adventageous derived traits of land plants
- cuticle: waxy surface that prevents excessive water loss
- secondary compounds: bitter tasting, strong odor or toxic effects that help defend against herbavores and parasites
- symbiotic associations between fungi and the first land plants: fungi helped first plants absorb nutrients bc they didnt have true roots
In what plants would we expect a vascular system?
ex: tall tree bc nutrients need to reach top leaves on that tree. vascular system is how
What term associates with non vascular plants?
- vascular plants can either be seed or seedless plants
Which type of plant is the most evolutionary successful?
angiosperms bc they have largest #of species they were able to diversify and gain adaptations
what is a seed?
- an embryo that has nutrients and parts that physically protect it
- 3 parts: embryo, nutrients, integument (protective coat)
What are some examples of seedless vascular plants?
- lycophytes (club mosses and relatives)
- pterophytes (ferns and relatives)
What are the 2 types of seed plants?
- gymnosperms: the naked seed plants including conifers, seed just thrown out there by wind etc
- angiosperms: the flowering plants. seed protected inside ovary which becomes fruit
What does the vascular system do?
moves fluids/nutrients throughout plant
In non vascular plants like bryophytes what is the dominant generation?
- sporophyte depends on gametophyte and is smaller
In vascular seedless plants, like ferns what is the dominant generation?
- gametophyte is smaller but independent
What are the types of bryophytes?
What are the gametophytes like on most mosses
- the archegonium and antheridia are on different gametophytes
- after the sporangium undergoes meiosis to produce spores they will develop either into a male or female gametophyte
Where do most mosses live, why?
moist environments bc water is needed for fertilization, limiting evolutionary success
Where do bryophyte sprophytes grow out of?
archegonia and are the smallest and simplest sporophytes of all surviving plant groups
What are stomata?
- regulate water and carbon dioxide. allows plants to decide when they want to lose water and take in co2. stomata can open or close.
- support photosynthesis
- present in all vascular plants
- some bryophyte sporophytes have them such as hornwart and moss
how does the sporophyte exist?
zygote divides by mitosis and becomes multicelular sporophyte
What are rhizoids?
- root like (but not roots) structures that are strictly support
- anchor gametophytes to substrate
Why are the gametophytes not very tall?
lack of vascular tissue
how is fertilization happening in bryophytes?
flagellated sperm swim to egg through water film
what is the ecological importance of mosses?
can help retain nitrogen in soil
Reproduction in seedless vascular plants?
- have flagellated sperm and like bryophytes are restricted to moist environments
- seedless plants can grow much taller tho bc of vascular system
What are main characteristics of living vascular plants?
- dominant sporophytes
- vascular tissues (xylem and phloem)
- well developed roots and leaves (true roots and leaves)
What are the 2 types of vascular tissue?
- xylem: dead cells and have lignen. transport water
- phloem: living cells, transport nutrients
Memorize all life cycles!!
Ferns, vascular seedless plants have what gametophytes?
they have both antheridium and archagonium on one gametophyte, bisexual
What is the sporangia?
- where the spores are produced by meiosis
- spores in vascular seedless plants are n so is gametophyte
- sporophyte is dominant in fern
What are roots?
- organs that anchor vascular plants and enable them to absorb water andnutrients from soil
- may have evolved from subterranian stems
What are leaves?
- organs that increase surface area of vascular plants
- enable plant to capture more solar energy for photosynthesis
What is homosporous?
- in sporophyte generation, 1 sporophyte type is produced and matures to both gametophytes (ex: ferns and most seedless vascular plants)
- bisexual gametophyte
What is heterosporous?
- homosporous species produce megaspores that give rise to female gametophytes and microspores that give rise to male gametophytes
- all seed plants and some seedless plants are heterosporous
What is the difference between meiosis in animals and plants?
- meiosis in animals: produces gametes
- meiossis in plants: produces spores
What are similarities between seedless vascular plants and bryophytes?
flagellated sperm that require moisture
What are differences between seedless vascular plants and bryophytes?
- lignified vascular tissue
- true roots and leaves
Whats wrong w/ the statement:
living charophytes are the algal ancestors of land plants
no, just the most closely related, they share a common ancestor
Whats wrong w/ the statement:
plant sporophytes grow from haploid spores
sporophyte generation comes by egg and sperm joining together by fertilization to form zygote 2n which divides by mitosis to form sporophytes (haploid spores generated from gametophytes)
Whats wrong w/ the statement:
Meiosis in plant life cycles results in the production of egg and sperm
- meiosis results in production of spores
- mitosis results in production of archegonium and antheridium which produce egg and sperm
Whats wrong w/ the statement:
bryophyte gametophytes are nutritionally dependent on the sporophyte generation
no sporophyte dependent on dominant larger gametophyte
How did seeds change the course of evolution?
enabled bearers to become dominant producers in most terrestrial ecosystems
What are the gametophyte and sporophyte like in seed plants
gametophyte microscopic and dependent on sporophyte(dominant)
What are the 5 key adaptations for seed plants to live on land?
- 1. reduced gametophytes (microscopic)
- 2. heterospory
- 3. ovules
- 4. pollen
- 5. seeds
What are advantages of reduced gametophytes?
- gametophytes of seed plants develop within walls of spores
- no drying out
- uv protection--> less harmful mutations
- nutrients obtained from sporophyte
What happens with heterospory in seed plants?
- megasporangia: 2n- produce megaspores (n) that give rise to female gametophytes
- microsporangis: 2n- produce microspores (n) that give rise to male gametophytes
What does an ovule consist of?
a megasporangium, megaspore, and one or more protective integuments (2n. outer protective tissue)
Where do pollen grains develop
- in the microspores
- pollen grains contain male gametophytes
- transfer of pollen to the part of a seed plant containing ovules
- pollen doesnt require h2o for fertilization
- if it germinates gives rise to a pollen tube that discharges 2 sperm into female gametophyte within ovule
Explain the development of a seed in a gymnosperm
- sporophyte generation starts
- megaspore expands and divides into female gametophyte by meiosis
- then female gametophyte produces egg by mitosis and pollen grain will find it and fertilize
- after fertilization you have the zygote which divides by mitosis to form embryo and there is still some tissue to provide embryo with nutrients
What are evolutionary adaptations of seeds?
- a seed is a sporophyte embryo
- can remain dormant for days to years bc they have nutrients unlike spores that cant as long bc they dont
- can be transported long distance by wind/animals
- seed coat more protective tan spore wall
What are the most prevelant gymnosperms?
- most can do photosynthesis year round and live 100s of years
Key features of gymnosperm life cycle
- dominance of sporophyte generation
- development of seeds from fertilized ovules
- transfer of sperm to ovules by pollen
What is the life cycle of a pine tree?
- pine tree is sporophyte and produces sporangia in male and female cones
- small cones produce microspores (pollen grains) each contains a male gametophyte
- the large cones contain ovules which produce megaspores that develop into female gametophytes
- takes nearly 3 years from cone production to mature seed
- fertilization can happen up to 1year after pollinization
What is the difference between gonad tissues and reduced gametophytes of seed plants
- gonad tissues: diploid and produce sperm and egg by meiosis
- plants: gametophytes are haploid and produce gametes by mitosis
What are the 3 generations of tissues in a seed
- gametophyte tissue (parent)
- integument (grandparent)
Know plant life cycle!! black and white one
What are reproductive adaptations of angiosperms
- reproductive structures: flowers and fruits
- flower is an angiosperm structure specialized for sexual reproduction
- can be pollinated by wind, insects or animals
What are the important structures in a flower?
- sepals: enclose flower
- petals: colors attract pollinators
- stamens: produce pollen on anthers
- carpels: produce ovules
What is a fruit?
- mature ovary
- protect seeds and aid in dispersal
What is the angiosperm life cycle?
- the flower of the sporophyte is composed of both male and female structures (bisexual)
- male gametophytes contained within pollen grains produced by mircrosporangia of anthers
- female gametophyte develops within an ovule contained in ovary at base of stigma (stigma recieves pollen)
- most flowers have mechanisms to ensure cross pollination btween flowers from diff plants of same species. increases diversity
In flower plants what happens with the microsproangium
- contains diploid microsporocytes that undergo meiosis to produce haploid microspores
- microspores divide by mitosis to produce male gametophyte (inside pollen grain) sperm will develop from one of these cells and the pollen tube from the other
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