Midterm 2 Flashcards
(344 cards)
1
Q
How long ago was the terrestrial surface lifeless?
A
~3BYA
2
Q
How long ago did Cyanobacteria develop?
A
~1.2BYA
3
Q
How long ago did small plants, fungi and animals develop?
A
500MYA
4
Q
How long ago did plants get taller?
A
385MYA
5
Q
Why did plants get taller 385MYA?
A
Access to more light
6
Q
How long ago did the earliest trees appear?
A
~385MYA
7
Q
What are the closest relatives to land plants?
A
Green algae called Charophytes
8
Q
What 3 traits did plants acquire independently?
A
1) Multicellularity
2) Photosynthetic pigments
3) Cell walls made of cellulose
9
Q
What are the 3 key traits that land plants share with charophytes?
A
1) Rings of cellulose-synthesizing proteins
2) Structure of flagellated sperm
3) Formation of phragmoplast
10
Q
What are phragmoplasts and what do they do in plants?
A
They are structures that guide assembly of the cell plate during cell division
11
Q
What is one adaptation that enabled plants to move to land?
A
Layer of durable polymer called sporopollenin which prevents zygotes from drying out
12
Q
What are 4 reasons for plants to move to land?
A
1) Unfiltered sun
2) More plentiful CO2
3) Nutrient-rich soil
4) Few herbivores or pathogens
13
Q
What are 2 issues plats had with moving to land?
A
1) Scarcity of water
2) Lack of structural support
14
Q
What would happen if the plant weren’t able to make an adequate amount of sporopollenin?
A
1) Zygotes would dry out
2) Spores would be less viable
15
Q
What is the word that we use to define plants with?
A
Embryophytes: plants w/ embryos
16
Q
What are 5 key traits of all plants
A
1) Alternation of generations: alternation b/w 2 multicellular stages: gametophyte (n) and sporophyte (2n)
2) Multicellularity
3) walled spores produced in sporangium: spore walls made of sporopollenin through meiosis of sporophyte
4) Multicellular gametangium: Archegonia (female organ) and Antheridia (male organ)
5) Apical meristems: responsible for extension of roots and shoots
17
Q
What are 3 more derived traits of plants?
A
1) Cuticle: waxy covering of epidermis
2) Mycorrhizae: fungi + land plants
3) Stomata: specialized spores that support photosynthesis by allowing gas exchange
18
Q
What are the 2 purposes of a waxy cuticle
A
1) Decreases water loss
2) Decreases microbial attacks
19
Q
What’s the purpose of Apical meristems?
A
Responsible for extension of roots and shoots
20
Q
What are the female and male gametangium organs that produce gametes called?
A
Female: Archegonia
Male: Antheridia
21
Q
How long ago did spores develop?
A
470MYA
22
Q
How long ago did spores with plant cuticle develop?
A
425MYA
23
Q
How are plants informally grouped?
A
They’re informally grouped by presence or absence of vascular tissue
24
Q
Which grouping of plants has the most diversity within their group?
A
Gymnosperms
25
Which grouping of plants is the most diverse?
Angiosperms
26
What are the four major groups of plants?
1) Bryophytes
2) Seedless vascular plants
3) Gymnosperms
4) Angiosperms
27
What are the 3 phyla within Bryophytes?
1) Hepatophyta: liverworts
2) Bryophyta: Mosses
3) Anthocerophyta: Hornworts
28
What are the 5 economic importances of Mosses?
1) Retains N in soils
2) Soil conditioner
3) Fuel source
4) Packing material
5) Storage of organic carbon
29
What are the 2 groups that seedless vascular plants are divided into?
1) Lycophytes
2) Monilophytes
30
What plants are in Lycophytes?
club mosses, spike mosses, quillworts + relatives
31
What plants are in Monilophytes?
ferns, horsetails, whisk ferns + relatives
32
What are the significances of the ancestors of Lycophytes?
They grew to great heights during the Devonian and Carboniferous eras, forming the 1st forests and creating coal. AND they may have contributed to global cooling as their roots increased the rate of calcium and magnesium which react with CO2.
33
What are the 2 groups of seed vascular plants?
1) Gymnosperms
2) Angiosperms
34
Did early vascular plants have dependent or independent sporophytes?
Independent branching sporophytes
35
What are 3 characteristics of living vascular plants?
1) Life cycles with dominant sporophytes
2) Vascular tissue called xylem and phloem
3) well-developed roots and leaves
36
What does xylem do?
It conducts most H2O and minerals and includes dead tube-shaped cells called tracheids
37
What does phloem do?
it consists of living cells arranged into tubes and distribute sugars, amino acids, and other organic products
38
What does vascular tissue provide to plants?
It gives plants increased height
39
What are 2 evolutionary advantages of having vascular tissue
They're taller so...
1) Get more sunlight
2) Spores dispersed faster
40
What are 2 functions of roots?
1) Anchors vascular plants
2) Enables vascular plants to absorb water and nutrients from the soil
41
What may have roots evolved from?
Subterranean stems
42
What's the function of leaves?
It increases surface area of vascular plants, thereby capturing more solar energy used in photosynthesis
43
What are the 2 categories of leaves?
1) Microphylls: leaves w/ single vein
2) Megaphylls: leaves w/ highly branched vascular system; present in all vascular plants except lycophytes
44
What's the definition of sporophylls?
Modified leaves with sporangium
45
What's the definition of Sori?
clusters of sporangium on the undersides of sporophylls
46
What's the definition of Strobili?
cone-like structures formed from groups of sporophylls
47
What are the characteristics of a heterosporous species?
They produce megaspores giving rise to female gametophytes and Microspores which give rise to male gametophytes
48
Are all seed plants and some seedless vascular plants hetersporous or homosporous?
Heterosporous
49
What are the characteristics of a Homosporous species?
They produce 1 type of spore that develops into a bisexual gametophyte
50
Are most seedless vascular plants Heterosporous or Homosporous?
Homosporous
51
What are monocots and Eudicots?
2 major groups of angiosperms
52
What 3 basic organs evolved in vascular plants?
1) Stems
2) Roots
3) Leaves
53
What are 3 important functions of roots?
1) Anchor plant
2) Absorb H2O and nutrients
3) Storing carbs
54
What's the function of the taproot system, and is it mostly monocots or eudicots that have them?
Tall plants with large shoot masses have taproot systems which prevents it from toppling. This includes most eudicots.
55
Describe what a primary root is
It's the first to emerge and it then branches to form lateral roots which improves anchorage and water storage.
56
What's the function of the fibrous system, and is it mostly monocots or eudicots that have them?
The fibrous root system consists of adventitious roots that arise from stems, leaves, and lateral roots. This includes most monocots.
57
Fibrous root system, monocot or eudicot?
monocot
58
Taproot system, monocot or eudicot?
eudicot
59
Where along the root does the most absorption occur?
Root hairs as they increase surface area of roots allowing for more absorption
60
what do axillary buds do?
structures that have the potential to form lateral shoot or branch
61
What is the apical bud?
growing shoot tip which causes elongation of young shoot
62
What's the function of apical dominance?
It helps maintain dormancy in most axillary buds
63
What are the 2 functions of plant stems?
1) structure
2) transport H2O and minerals
64
What are the 4 functions of leaves?
1) Intercept light
2) Exchange gasses
3) Dissipate heat
4) Defend plant from herbivores and pathogens
65
What kind of veins do monocots have?
Parallel veins
66
What kind of veins do Eudicots have
branching veins
67
When classifying angiosperms by their leaves, what are the 2 categories?
1) Simple
2) Compound
68
What does each plant organ have (3 things)?
Dermal, vascular, and ground tissues and each forms a tissue category
69
In non-woody plants what does the dermal tissue consist of?
epidermis
70
In non-woody plants, what is the function of the waxy coat/cuticle?
prevents water loss from epidermis
71
In non-woody plants, what is the periderm?
It's protective tissue that replaces epidermis in older regions
72
In non-woody plants what are trichomes and what are its functions?
outgrowths of shoot epidermis which helps reduce water loss and insect defense
73
What are the 2 types of vascular tissue in non-woody plants and what are their functions?
Xylem: transports H2O and dissolved minerals from roots to shoots
Phloem: transports organic nutrients from sources to sinks (sugar)
74
What are the vascular tissues of stem and root in non-woody plants?
stele: central part of the root or stem
75
In angiosperms what is the stele of a root?
It's a solid central vascular cylinder
76
In non-woody plants, what does the ground tissue system consist of?
-Internal to vascular tissue: pith
-Eternal to Vascular tissue: cortex
-Includes specialized cells for storage, photosynthesis, support and transport
77
What are the 5 types of plant cells?
1) Parenchyma
2) Collenchyma
3) Sclerenchyma
4) Water-conducting cells of the xylem
5) Sugar-conducting cells of the phloem
78
What are the characteristics and functions of Parenchyma cells?
Mature: thin flexible primary walls, lack secondary walls, are least specialized, perform most metabolic functions, and retains ability to divide and differentiate
79
What are the characteristics and functions of Collenchyma?
-Grouped in strands and help support young parts of plant shoot
-Have thicker and uneven cells walls
-Provide flexible support without restraining growth
-Flexibility and support
80
What are the characteristics and functions of Sclerenchyma?
-Rigid due to thick secondary walls strengthened with lignin, and are dead at functional maturity
-2 types:
1) Sclereids: short irregular shape w/ thick lignified secondary walls
2) Fibers: long and slender and arranged in threads
81
What are the characteristics and functions of Water-Conducting cells of the xylem?
-2 Types: Tracheids and Vessel Elements
-Tracheids: found in xylem of all vascular plants
-Vessel Elements: common to most angiosperms + some gymnosperms; they align end to end to form long micro pipes called vessels
-Sieve-tube elements: alive at functional maturity, but lack organelles
-Sieve plates: has a companion cell whose nucleus and ribosomes serve both cells
82
Where are tracheids found?
Found in xylem of all vascular plants
83
Structure of meristematic tissue?
1) Top: Apical meristem
2) middle: Intercalay meristem
3) bottom: Lateral meristem
84
What are the 2 different types of growth?
1) Indeterminate growth: grow throughout life
2) Determinate growth plant organs cease to grow at certain age
85
What are meristems and what do they allow for?
They're perpetually embryonic tissue allowing for indeterminate growth
86
What are the 2 types of meristems?
Apical and lateral
87
Where are apical meristems found and what is their function
They're located at tips of roots and shoots and at axillary buds. They elongate shoots and roots in process of primary growth (vertical)
88
What's the function of lateral meristems?
add thickness to woody plants in process of secondary growth (lateral)
89
What are the 2 types of lateral meristems?
Vascular cambium and cork cambium
90
What's the function of vascular cambium?
adds layers to vascular tissue called secondary xylem (wood) and secondary phloem
91
What's the function of cork cambium?
replaces epidermis w/ periderm, which is thicker and tougher
92
What are 2 things that meristems give rise to?
1) Initials: stem cells that remain in the meristem
2) Derivatives: become specialized in mature tissue
93
What does the term annuals mean for flowering plants?
Complete lifecycle in year or less
94
What does the term biennials mean for flowering plants?
require 2 growing seasons
95
What does the term perennials mean for flowering plants?
live for many years
96
Primary growth: What's the purpose of a root cap?
It protects the apical meristem as root pushes through soil
97
Primary growth: What 3 zones does growth occur behind the root tip?
1) Zone of cell division
2) Zone of elongation
3) Zone of differentiation and maturation
98
Primary growth: Where do lateral roots arise from?
arise from within the pericycle, the outermost cell layer in vascular tissue
99
Primary growth: What is the function and name of the innermost layer of the outer layer in vascular tissue?
Endodermis: regulates passage from soil into vascular cylinder
100
What does primary growth of roots look like in Eudicots?
xylem is starlike w/ phloem b/w the arms
101
What does primary growth of roots look like in monocots?
core of parenchyma cells is surrounded by rings of xylem then phloem
102
Primary growth of shoots: where do leaves develop from?
Leaf primordial along apical meristem
103
Primary growth of shoots: where do lateral shoots develop from?
axillary buds on stem's surface
104
What does primary growth of shoots look like in monocots?
vascular bundles are scattered throughout the ground tissue
105
What does primary growth of shoots look like in Eudicots?
vascular tissue consists of vascular bundles arranged in a ring
106
What are the functions of stomata in leaves?
they are pores that allow CO2 and O2 exchange, and they are also major avenues for evaporative water loss
107
What is the purpose of guard cells?
they stretch and close the stomata
108
What is secondary growth a characteristic of? (monocots or eudicots, gymnosperms or angiosperms)
Characteristic of gymnosperms and angisperms and many eudicots, but NOT monocots
109
Why does secondary growth only occur in stems and roots of woody plants and not in leaves?
Secondary growth provides thickness which would be bad for leaves
110
What does secondary growth consist of?
consists of tissues produced by the 2 types of lateral meristems: vascular cambium and cork cambium
111
True of false: Primary growth and secondary growth occur simultaneously?
TRUE
112
What is dendrochronology used for and what does it study?
It's the science that deals with the dating and study of the annual growth increments, or tree rings, in woody trees and shrubs
113
Do older layers of secondary xylem still transport H2O?
NO
114
Do outer layers of secondary growth known as sapwood still transport H2O?
YES
115
If bark is vut off in a ring around the tree, why does a bubble form?
Transport of water and nutrients continues where bark was not cut
116
Which plant revealed how secondary growth was triggered?
Arabidopsis plant
117
What is the cue for wood formation (secondary growth)?
Stem weight
118
Define growth:
an irreversible increase in size
119
Define Morphogenesis:
development of body form and organization
120
Define cell differentiation:
the process by which cells w/ same genes become different from each other
121
How tall did the tallest red cedar get?
115.7 meters
122
What is the major limitation of tall trees like red cedar?
Hydraulic limitation = major limiting factor for tall trees
123
How does transport through phloem work?
transport brings products from sources to sinks via translocation
124
What are the functions of stems?
serve as conduits for water and nutrients and as support structures for leaves
125
What does length and branching in shoots affect and what is a common trade off?
Length and branching pattern affect light capture; trade off b/w growing tall and branching
126
What is phyllotaxy and why is it important?
It's the arrangment of leaves on stem which is important for light capture
127
What phyllotaxy do most angiosperms have?
alternate with spirally arranged leaves
128
Why are leaves so thin?
Green leaves are thin and broad to increase the surface area for absorption of light and carbon dioxide
129
Do horizontal leaves capture more light in low-light conditions or sunny conditions?
low-light
130
Why are vertical leaves more favourable in sunny conditions?
It's because they're less damaged by the sun and lower leaves can get light
131
What are the 3 transport routes for water and minerals?
1) Apoplast route: through cell walls and extracellular spaces
2) Symplast route: through cytosol
3) Transmembrane route: across cells
132
What consists of the Apoplast pathway?
everything external to plasma membrane; cells walls, extracellular space, and interior of vessel elements and tracheids
133
What consists of the Symplast pathway?
consists of cytosol of living cells in plants as well as plasmodesmata
134
What characteristic of the plasma membrane controls short-distance transport?
permeability
135
What are 4 short-distance ways of transporting solutes across the plasma membrane in plants?
1) Proton pump: membrane potential established by pumping H+ which in turn establishes a pH gradient driving transport of solutes
2) H+/sucrose Cotransporter: energy from H+ gradients used to cotransport ions by active transport. Example: Sugar in phloem
3) H+/NO3- Cotransporter: energy from H+ gradients used to cotransport solutes by active transport. Example: important in for uptake of NO3- in root cells
4) Ion Channels: only allow certain ions to pass. Example: K+ ion channel involved in release of K+ from guard cells when stomata close
136
How is water transported over short distances in plants?
Osmosis: plants must balance water uptake and loss to survive and they do so by osmosis. It's the diffusion of water into or out of the cell affected by solute concentration and pressure
137
What happens if a flaccid/isotonic plant cell is placed in a hypertonic solution?
Plasmolysis: occurs when the protoplast shrinks and pulls away from the cell wall
138
What happens if a flaccid/isotonic plant cell is placed in a hypotonic solution?
Turgid
139
What do aquaporins do in plant cells in relation to short distance water transport?
they are transport proteins in cell membrane` that facilitate passage of H2O; these affect the rate of water movement across the membrane
140
With what mechanism is water transported over long distances in plant cells?
Bulk flow
141
How does Bulk flow via the xylem work?
Transports xylem sap, water and dissolved minerals, from roots to leaves. Bulk flow is driven by transpiration (evaporation of water from plant's surface) and doesn't require energy
142
What are the 4 differences between bulk flow and diffusion?
1) Bulk flow driven by pressure potential not solute potential
2) Bulk flow occurs across hollow dead cells not across living cell membranes
3) Bulk flow moves entire solution not just water and solutes
4) Bulk flow is much faster
143
What is the cohesion-tension hypothesis?
Transpiration and water cohesion pull water from roots to shoots; movement of xylem sap against gravity is maintained by the cohesion-tension mechanism
144
What is transpirational pull and how does it work?
water from air spaces in leaf evaporates causing air-water interface to retreat further into the mesophyll cell causing negative pressure. This negative pressure pulls water in the xylem into the leaf.
145
Transpirational pull on xylem sap goes from where to where?
leaves to roots
146
How does adhesion and cohesion work in plant cells long distance transport in xylem?
water molecules attracted to cellulose in xylem cell walls through adhesion. Adhesion of H2O to xylem cell walls helps offset the force of gravity
147
How does bulk flow via positive pressure work and in what kind of vascular tissue does it occur?
It occurs in the phloem as sap moves from sieve tube by bulk flow by positive pressure called pressure flow
148
True or False: Xylem is one way flow and negative pressure and Phloem is 2 way flow and positive pressure
TRUE
149
What rate is regulated by stomata?
The rate of transpiration is regulated by stomata
150
What are the functions of guard cells which flank stomata?
They open and close the stomata., helping balance water conservation with gas exchange for photosynthesis. When turgid, pore opens, and when flaccid, pore closes; this results primarily from reversible uptake and loss of K+ by guard cells
151
What ion is the most responsible for causing the guard cells to be flaccid and turgid?
K+
152
What percentage of water is lost via the stomata?
95%
153
What 3 conditions could cause stomata to close during the day?
drought, high temps, and wind
154
What hormone produced in response to water deficiency causes stoma to close at dawn?
Abscisic acid (ABA)
155
What 4 conditions will cause stoma to close?
1) light
2) CO2 depletion
3) An internal "clock" in guard cells; circadian rhythm
4) water loss
156
What kind of plants have developed adaptations for living in arid clinates?
xerophytes
157
What are 7 adaptations developed by a wide range of plants to reduce water loss?
1) thick cuticles
2) thin waterproof waxy cuticles
3) taproots
4) Some desert plants complete their lifecycle during rainy season
5) Some desert plants have fleshy stems to store water
6) Some plants have leaf modifications to reduce rate of transpiration
7) specialized form of photosynthesis called CAM where stomatal gas exchange occurs at night
158
What angle b/w leaves is best and why?
137.5 degrees and it minimizes shading on lower leaves
159
How do roots adjust to local cconditions?
they branch more in high nitrate soils than in low nitrate soils
160
True or false: roots are more competitive with roots of same plant?
FALSE; Less competitive
161
Why do some plants resort to carnivory?
They live in nutrient poor soils and use carnivory to obtain mineral nutrients
162
What’s an example of the corkscrew carnivore?
Genlisea; uses modified underground leaves to capture soil organisms and hairs lining the leaves ensures one-way passage
163
Which layer of soil do plants obtain most water and minerals?
Upper layers of soil (Topsoil/A Horizon)
164
What are 2 important features of soil?
Texture and composition
165
What 3 things does topsoil consist of?
Minerals, living organisms, and humus
166
What is the composition of topsoil?
Contain equal amount of sand, clay, and silt
167
What do inorganic components such as cations do in soil?
They adhere to negatively charged soil particles, preventing them from leaching out of the soil through percolating groundwater
168
What are 3 things organic components of soil such as humus do?
1. Builds crumbly soil that retains H2O,
2. increases capacity to exchange cation
3. serves as reservoir of mineral nutrients
169
Through what process do nutrients get into roots?
Cation exchange: cations displaced from sol particles by other cations, particularly H+, enter the soil solution and can be taken up by rots
170
What part of the root achieves cation exchange?
Root hairs
171
What are 3 consequences of intensive agriculture?
1) Depletes mineral content in soil
2) Taxes water reserves
3) Encourages erosion
172
What percentage of farmland has reduced productivity due to soil mismanagement?
30%
173
What are the 7 functions of Soil for plants?
1) Anchorage
2) Nutrient source
3) Water retention
4) Gas exchange (particularly O2)
5) Microbial interactions helping with nutrient cycling
6) Physical protection
7) pH and soil exchange
174
What is the primary source of irrigation waters?
Aquifers
175
What 2 things can happen with the depletion of aquifers?
1) Results in subsidence; settling and sinking of land
2) Salinization
176
What form of irrigation is better?
Drip irrigation; less water and reduces salinization while providing more water to plants
177
What does fertilizer do?
Replaces depleted nutrients
178
What can excess minerals in fertilizers cause?
Algal blooms
179
What are organic fertilizers composed of?
Composed of manure, fish meal, or compost which release N, P and K as they decompose
180
What do commercial fertilizers contain?
N, P and K
181
What percentage of global freshwater is used for agriculture
75%
182
What does soil pH affect?
It affects cation exchange and chemical form of mineras
183
What are 4 solutions to control erosion? (Topsoil loss due to wind and water)
1) planting trees as windbreakers
2) terracing hillside crops
3) cultivating in a contour pattern
4) practicing no-till agriculture
184
What is phytoremediation?
Reclaims contaminated areas suing plants capable of extracting soil pollutants
185
What percentage of plant’s fresh mass is H2O?
80-90%
186
What percentage of a plant’s mass is inorganic substances from soil?
4%
187
What percentage of a plant’s dry mass comes from CO2 assimilated into carbs?
96%
188
What is the purpose of hydroponic cultures?
Helps determine what chemical elements are essential
189
How many nutrients are essential for a plant to complete their life cycle?
17
190
What are the 9 macronutrients (need in large amounts)?
Carbon, Oxygen, Hydrogen, Nitrogen, Phosphorous, Sulfur, Potassium, Calcium, and Magnesium
191
What are the 8 micronutrients (need in small amounts)?
Chlorine, Iron, Manganese, Boron, Zinc, Copper, Nickel, and Molybdenum
192
When mineral concentrations are higher inside root cells than in soil, what do plants need to do in order to bring in more?
Hydrolyze ATP in order to bring nutrients into the roots against their gradient
193
In what kind of leaves are mineral deficiencies most common?
Maize leaves
194
What are 2 modifications to plants?
1) resistance to aluminum toxicity: bacterial gene allowing plant to secrete acids that bind to free aluminum
2) smart plants: inform grower of nutrient deficiency w/ change in colour
195
What does aluminum do to crops?
Damages roots and reduces crop yield
196
What are 5 mutualistic relationships b/w plants and other organisms?
1) Plants and soil microbes
2) Plants with Rhizobacteria and Endophytes
5) plants and Nitrogen fixing Bacteria
6) Plants and fungi
7) Plants and vertebrates
197
What 4 things do Rhizobacteria and Endophytes give plants?
1) Produces chemical that stimulate plant growth
2) Produces antibiotics that protects from disease
3) Absorbing oxide metals
4) increasing nutrients
198
How do Bacteria help plants?
Turn nitrogen gas from atmosphere into NO3- or NH4+
199
What are nodules in relation to bacteria and plants mutualistic relationship?
Composed of plant cells infected by nitrogen-fixing bacteria; hey fix N and receive sugar
200
How do fungi help plants?
Mycorrhizae = fungi and plant roots
Plant receives increase in surface area and they also secrete growth factors hat stimulate root growth and branching
201
How do vertebrates help plants?
In coastal regions likeBC, salmon are dragged into the forest by predators providing Phosphorous to plants
202
What are3 examples of non-mutualistic plants?
1) Epiphytes: grows on plants
2) parasitic plants: absorb sugar ad minerals from living host plant
3) Carnivorous plants: photosynthetic but obtain N from insects
203
What’s an example of a parasitic plant?
Rafflesia (also biggest flower)
204
In angiosperms is it the gametophyte or sporophyte that we see?
Sporophyte
205
What are the 3 F’s that characterize angiosperm life cycles?
1) Flower
2) double Fertilization
3) Fruits
206
What are the 4 floral organs?
1) Carpels
2) Stamens
3) Petals
4) Stepals
207
What are stamens and carpels?
Reproductive organs
208
What’s the structure of a stamen?
Filament topped by an anther
209
What’s the structure of carpels?
Long style with a stigma which pollen may land
210
What is a group of fused carpels called
A pistil
211
What is a slugger of flowers called
Inflorescences
212
What is pollination?
The transfer of a pollen from an anther to a stigma
213
What are the 3 methods of transferring pollen from an anther to a stigma?
1) wind
2) water
3) animals
214
What % of angiosperms are wind-pollinated?
~20%
215
What % of flowering plants are pollinated by insects?
~65%
216
Which insect is the most important pollinator?
Bees
217
Define coevolution
Joint evolution in response to selection imposed by each other
218
What is an example of coevolution that Darwin predicted?
Darwin correctly predicted a moth w/ a 28cm long tongue based on the morphology of a particular flower
219
What are the 4 steps in an angiosperms lifecycle?
1) Gametophyte development
2) Pollination
3) doubling fertilization
4) seed development
220
What are 2 characteristics of angiosperm gametophytes?
1) Microscopic
2) development obscured by protective tissue
221
What does pollen develop from?
they develop from microspores within the microsporangium, or pollen sacs of the anthers
222
Each microspore undergoes mitosis to produce what 2 cells?
1) Generative cell
2) Tube cell
223
Where does the female gametophyte of angiosperms develop?
within the ovule
224
What surrounds the megasporangium in an ovule?
integumentary
225
1 cell in the megasporangium undergoes meiosis to 4 megaspores, how many survive?
1
226
What happens to the single surviving megaspore?
It divides without cytokinesis, producing 1 large cell w/ 8 nuclei, then it's partitioned into a multicellular female gametophyte, the embryo sac
227
How does double fertilization work?
2 sperm reach the female gametophyte. 1 fertilizes egg and other combines w/ 2 polar nuclei giving rise to the triploid food-storing endospore (3n)
228
What does double fertilization ensure?
ensures that the endosperm only develops in ovules containing fertilized eggs
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What occurs after double fertilization?
seed development; each ovule develops into a seed and the ovary develops into the fruit enclosing the seed
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When a seed germinates, what does the embryo develop into?
A new sporophyte
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What part of the female gametophyte in angiosperms develops into the fruit?
The ovary
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What are the 6 steps in seed development?
1) Endosperm development
2) Embryo development
3) Seed dormancy
4) Seed germination
5) Seedling development
6) Flowering
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When does endosperm development occur? And what does the endosperm store?
It usually precedes embryo development. In most monocots and eudicots, the endosperm stores nutrients that can be used by seedling
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What does embryo development entail?
The 1st mitotic division of the zygote splits the fertilized egg into the basal cell and a terminal cell.
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What does the basal cell produce?
The basal cell produces a multicellular suspensor which anchors the embryo to the plants
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What is the hypocotyl of plants?
it is the stem of a germinating seedling, found below the cotyledons (seed leaves) and above the radicle (root)
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Why do some eudicot seeds have thin cotyledon?
Because they retain food in their endosperm; it also absorbs nutrients from the endosperm and transfers then to the rest of the embryo when the seed germinates
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What % of a mature seed is water?
5-15%
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How many cotyledons do monocot embryos have?
they have 1 cotyledon; grasses such as maize and wheat have a special cotyledon called a scutellum
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What's the name of the special cotyledon possessed by maize and wheat?
Scutellum
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What is seed dormancy for?
increases the chance that germination will occur at a time and place most advantageous to the seedline
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What environmental cues are required for breaking of the seed to occur?
temp or lighting changes
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What does seed germination depend on?
imbibition: the uptake of water due to low H2O potential of a dry seed
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What's the order in which the seedline develops?
1) radicle emerges
2) developing root anchors the plant
3) shoot breaks through the soil
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How does Eudicot seed germination occur?
a hook forms in the hypocotyl, and growth pushes the hook above ground. Light causes the hook to straighten an pull the cotyledons and shoot tip up
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What is the coleoptile?
Cylindrical organs that ensheath the first leaf and shoot apex in grass seedlings
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How does Monocot seed germination occur?
the coleoptile pushes up through the soil creating a tunnel for the shoot tip to grow through
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What kind of angiosperms do maize and other grasses fall into?
Monocots
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Why are flowers of a given plant species synchronized in their appearance at a specific time during the year?
To promote outbreeding
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What is flowering triggered by?
A combination of environmental cues and internal signals
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What is the carpel of a flower?
The female reproductive organ that contains an ovary, a stigma, and a style
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What are fruits classified by and what are the 4 groups?
they're classified by their development
1) Simple fruits: develop from a single or several fused carpels
2) Aggregate fruits: result from a single flower w/ multiple separate carpels
3) Multiple fruit: develop from a group of flowers (inflorescence)
4) An accessory fruit: contains other floral parts in addition to ovaries
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What is the advantage of asexual reproduction (vegetative reproduction) in angiosperms?
Good for plants in stable envs
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What is the disadvantage of asexual reproduction (vegetative reproduction) in angiosperms?
vulnerable to local extinction if there's any environmental change
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What is the advantage of sexual reproduction in angiosperms?
generates genetic variation that makes evolutionary adaptation possible
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What is the disadvantage of sexual reproduction in angiosperms?
Only a fraction of the seed survives
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Why do plants self fertilize?
to ensure every ovule develops into a seed
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What are 4 mechanisms to prevent self fertilization "Selfing"?
1) Dioecious species = staminate and carpellate flowers on diff. plants
2) Self-incompatibility is the ability to reject its own pollen
3) Some plants reject pollen w/ S-gene matching allele in stigma cells
4) Recognition of self blocks pollen tube growth
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Which mechanism to prevent selfing is the most common?
Self incompatibility: ability to reject its own pollen
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Where is light sensed to initiate phototropism in grass seedlings?
Tip of the coleoptile which contains a blue light sensor
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What mechanism/hormone allows the plant to bend?
The phototropic signal is a chemical that causes the coleoptile tip to bend due to the elongation of the cells on the side where light isn’t hitting, that way the plant bends towards the light
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What is the Hormone hypothesis proposed by the Darwins for phototropism?
“some matter in the upper part which transmits its effects to the lower part”
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What are the 3 evidences that support the hormone hypothesis for phototropism?
1) Coleoptiles bend in response to light if substances from the tip are allowed to move downward
2) If bending can take place in the darkness, then light isn’t directly required for réponse. Only hormone is required
3) During phototropic response, bending occurs bc cells on shaded side of coleoptile elongate
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What gene was found by analyzing mutant arabidopsis thaliana individuals that don’t show a phototropic response to light?
PHOT1
265
What is photomorphogenesis?
The effects of light on plant morphology
266
What wavelengths of light induce curvature?
Only wavelengths below 500nm
267
What causes different plant responses to light?
These responses can be mediated by the same or different photoreceptors
268
What are the 2 major classes of photoreceptors?
1) Blue-light receptors: controls hypocotyl elongation, stomatal opening and phototropism
2) Phytochromes: contain pigments that mostly absorb red light and regulate seed germination and shade avoidance
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Hypocotyl?
Stem of a germinating seed
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What’s the difference between red light and far-red light effects?
Red light increases germination while far-red light inhibits it. The final light exposure determines response
271
What is a photoperiod?
The relative lengths of night and day and it is the environmental stimulus plants use most often to detect time of year
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What is photoperiodism and what does it control?
It’ the physiological response to photoperiod, and flowering is controlled by photoperiodism
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When do short-day plants flower?
When light is shorter than a critical length of light
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When do long-day plants flower?
When light period is longer than a certain # of. Hours
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Is it day length or night length that controls responses to photoperiod?
Night length
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How are short-day plants governed by night length?
They’re governed by whether the critical night length sets a minimum # of hours of darkness
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How are long-day plants governed by night length?
They’re governed by whether the critical night length sets a maximum # of hours of darkness
278
What is vernalization?
Cold pretreatment: it’s an example of flowers requiring additional environmental stimulus on top of the photoperiod in order to flower
279
With what organ do leaves detect photoperiod?
Photoperiod is detected by leaves which cue buds to develop into flowers
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What is the hypothetical flowering hormone and what is the evidence for this hormone?
The hormone is called florigen
Evidence: a signal from a grafted leaf can induce flowering
281
What is geotropism/gravitropism?
Response to gravity
282
What is the statolith hypothesis in gravitropism?
It states that plants may detect gravity by the settling of statoliths, dense cytoplasmic components
283
What type (positive or negative) of gravitropism do roots and shoots demonstrate?
Roots: positive
Shoots: negative
284
What is thigmomorphogenesis?
Changes in form that result from mechanical disturbance
285
What is an example of thigmomorphogenesis?
Rubbing stems of young plants a couple of times daily results in plants that are shorter than controls
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What is Thigmotropism? And in what plants does it occur?
Growth in response to touch which occurs in vines and other climbing plants
287
What does flooding do to plants?
Results in enzymatic destruction of root cortex which creates air tues that help plants survive oxygen deprivation during flooding
288
What does drought do to plants?
They reduce transpiration by closing stomata, reduce exposed surface area and shedding leaves. Growth of shallow roots is inhibited and deeper roots continue
289
What does heat stress do to plants, and what is something that helps protect against this?
Heat stress can denature a plant’s enzymes. Transpiration helps cool plants leaves by evaporative cooling. AND heat-shock proteins help protect other proteins against heat stress
290
What kind of proteins help other proteins in plants during heat stress?
Heat-shock proteins
291
What does salt stress do to plants and what is the plants response?
Salt can lower the water potential of the soil solution and reduce water uptake. In response, plants produce certain solutes at high concentrations which keeps the water potential of cells more negative than that of the soil solution
292
What does cold stress do to plants and how do plants prevent this?
Cold decreases membrane solubility. Altering lipid composition is a response to cold stress. Many plants have anti-freeze proteins to prevent ice formation and damage to cells
293
How do plants defend against herbivores?
Physical defenses: thorns and trichomes
Chemical defenses: distasteful or toxic compounds
Mind-altering: some plant products cause mind-altering effects.
Plants damaged by insects release volatile chemical to warn other plants
294
What is an amino acid that plant produce that kills insects upon digestion?
Canavanine
295
What’s the first line of defence against pathogens in plants?
The epidermis and periderm, but they can still enter through wounds or natural openings like stomata.
296
How is PAMP immunity triggered?
Once PAMPs are recognized, a chain of signalling events start leading to the production of anti microbial chemicals and toughening of cell wall
297
What does PAMPs stand for?
Pathogen associated molecular patterns
298
True or False: PAMPs are specific to certain pathogens?
TRUE
299
What mechanism did pathogens evolve in order to suppress PAMP-triggered immunity?
Pathogens developed the ability to deliver effectors into plant cells which suppress PAMP-triggered plant immunity
300
What are effectors that pathogen sinsrt in plant cells, and what do they do to the plant cell?
Effectors or pathogen-encoded proteins that cripple a host’s innate immunity system
301
What is the plant’s defence against effectors?
plant defence results from action of hundreds of disease resistant (R) genes. Each R-protein is activated by a specific effector. R-proteins trigger signal transduction pathways leading to local and general response
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What are the 4 hypersensitive responses (Local responses) that result from R-gene triggering transduction pathways?
1) stomatal closure
2) production of toxin
3) Reinforcement
4) rapid suicide of infected cells
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How is the general response triggered in plants?
The hypersensitive response (local response) produces a signal that induces Systemic Acquired Resistance (SAR)
304
What are the 8 major plant hormones needed for growth and development?
1) Auxin
2) Cytokinins
3) Gibberellins
4) Abscisic acid
5) Ethylene
6) Brassinosteroid
7) Jasmonates
8) Strigolactones
305
What is the major type of Auzin in plants?
Indoleacetic acid (IAA)
306
What does Auxin as a term refer to?
refers to any chemical that promotes elongation of coleoptiles
307
What are the 2 roles of Auxin?
1) Elongation
2) Alters gene expression and stimulates a sustained growth response
308
What is the hypothesis for how auxin plays a role in elongation of coleoptiles?
Acid growth hypothesis states that auxin stimulates proton pumps in the plasma membrane. The proton pumps lower pH of cell wall, activating expansins, enzymes that loosen the wall's fabric. Then cell elongates.
309
Why were cytokinins named this?
It's because they stimulate cytokinesis (cell division)
310
When are cytokinins produced?
they're produced in actively growing tissues such as roots, embryos, and fruit
311
What are the 3 functions cytokinins play?
1) cell division and differentiation (w/ auxin)
2) Apical dominance (w/ auxins and strigolactones)
3) Anti-aging
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What are the 3 things that cytokinins do to slow the aging process of some plant organs?
1) Inhibit protein breakdown
2) Stimulating RNA and protein synthesis
3) Mobilizing nutrients from surrounding tissue
313
Which hormone causes Foolish seedling disease?
Caused by Gibberella fijikuroi (fungus) which produced Gibberellins causing plants to grow excessively tall and thin
314
What 3 roles do Gibberellins play?
1) Growth of stems and leaves; In stems they trigger cell elongation and cell division
2) Fruit growth (w/ auxin)
3) Germination: after water is imbibed, release of gibberellins signals seeds to germinate
315
Where is auxin produced and where is it transported to?
Produced in shoot tips and transported down the stem
316
What is the major role of abscisic acid in plants?
It regulates growth, development, and stress responses within plants, specifically through inhibition of cell division
317
What are 2 of the many effects of abscisic acid?
1) Seed dormancy: ensures that seed will germinate only in optimal conditions
2) Drought tolerance: ABA is the primary internal signal that enables plants to withstand drought. An accumulation of ABA causes stomata to close rapidly.
318
What is precocious and what is it caused by?
It is early germination which can be caused by inactive or low levels of ABA
319
What is Ethylene produced in response to?
produced in response to stress such as drought, flooding, mechanical pressure, injury, and infection
320
What response does ethylene induce when a plant is under mechanical stress?
It induces the triple response which allows growing shoot to avoid obstacles. This response consists of a slowing of stem elongation, a thickening of the stem, and horizontal growth
321
What is senescence and what is it triggered by?
It is programmed cell or organ death often associated with a burst of ethylene
322
What causes leaf abscission?
change in balance of auxin and ethylene
323
What causes fruit ripening?
A burst of ethylene production triggers the ripening process. Ethylene triggers ripening which triggers release of more ethylene (positive feedback loop)
324
What kind of feedback loop is the process of fruit ripening?
Positive: this is because ripening is caused by a burst of ethylene then ripening triggers release of more ethylene
325
How old is the earliest Homo Sapien fossil?
196,000 years old
326
What were important staples in hunter-gatherer diets?
wild plants, fungi and animals
327
Who are the San?
They're amongst the 1st people to have lived in southern africa and they're one of the few hunter-gatherer societies
328
How many hours per week do the san spend gathering food from the wild?
12-19 hours
329
What are the 4 hypotheses used to explain the shift from hunter-gatherer to agriculture?
1) Changes in climate causing reduction in wild food sources
2) Greater pop density increasing food demand
3) Overhunting leading to decline in wild prey pops
4) Changing tech like domesticating seeds making agriculture a more viable lifestyle
330
How many years has agriculture been practiced?
Practiced sporadically for the past 13,000 years
331
Where did agriculture start independently (3 places)?
1) Northern China
2) Central America
3) Fertile Crescent
332
What were the 4 types of first crops?
1) Wheat
2) Barley
3) Lentils
4) Types of peas
333
What is crop domestication?
artificially selecting plants to increase their suitability to human requirements: taste, yield, storage, and cultivation practices
334
What are 4 features of domestication syndrome?
1) Loss of dispersal
2) Increase in size
3) Loss of seed dormancy
4) Loss of chemical or mechanical protection against herbivores
335
What was the great Famine and how much did the Pop fall?
Period of starvation in Ireland from 1845-1852. 1 million died and over 1 million fled causing pop to fall by 20-25%
336
What is a Canadian invention?
Canola oil derived from rapeseed
337
What is hybridization used for?
It's common in nature and has been used by breeders to introduce new genes
338
How are mutations used in breeding plants?
they arise spontaneously and plants with beneficial ones are used in breeding experiments
339
What are the 2 uses of the word Plant Biotechnology?
1) refers to innovations in the use of plants to make useful products
2) Specifically refers to use of GM organisms in agriculture and industry.
340
What are transgenic organisms?
those who have been engineered to express a gene from another species
341
What are 3 benefits of transgenic crops?
1) Produce proteins (Bt toxic) to defend against insect pests
2) Tolerate herbicides
3) Resist specific diseases
342
What is being improved in plants?
Nutritional quality of plants is being improved
343
What is Golden rice?
Transgenic variety being developed to address vitamin A deficiencies amongst the world's poor
344
how is cassava being engineered?
developed w/ increased levels of Fe and beta-carotene
