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Sem 2 > Bio Midterm 1 > Flashcards

Bio Midterm 1 Flashcards

1
Q

What is the role of xylem and phloem?

A

Xylem:
- Interior tissue that’s responsible for the transport of water and nutrients from roots to leaves to replenish the water vapour lost through stomata
- Elongate during development
- Tracheids (gymno) are unicellular conduits
- Vessels (angi) are multicellular conduits

Phloem:
- Outside tissue, transports carbs from leaves to rest of plant
* Source-to-sink transport of carbs, amino acids, ions, hormones etc
* Turgor in sink is low and in source is high, the pressure difference drives movement

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2
Q

Source vs Sink parts of plants

A

Source:
- Happens in photosynthetic parts of plants
- Responsible for synthesising the sugars required for plant growth
- E.G Leaves

Sink:
- The areas of active growth and the areas of storage
- Use the sugars for immediate use and store the rest for future metabolic needs.
- E.G Seeds, flowers, roots

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3
Q

What makes up the thick cell walls of plants:

A

Sclerenchyma which are tightly packed lignified cells full of cellulose. Provide mechanical strength and support

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4
Q

Describe Crassulacean Acid Metabolism (CAM) photosynthesis

A
  1. Stomata open at night
  2. CO2 enters
  3. Combines with PEP to form malate
  4. Malate stored in vesicles until day
  5. Malate is decarboxylated
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5
Q

What’re the two limiting nutrients for plants?

A

Nitrogen and phosphorus

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6
Q

Describe Cation Exchange Capacity (CEC)

A
  • Soil particles have negatively charged ions
  • Positively charged ions in water attach to soil particles, they swap nutrients
  • CO2 must be in water
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7
Q

Define endodermis

A

Layer of cells surrounding root
vascular tissues, selective controls which
materials enter xylem

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8
Q

Describe the process of root uptake

A
  1. Nutrients pass through plasmodesmata into xylem or through the intercell water creeks that go out the root tips
  2. To enter the xylem the casperian strips prevent water from passing through endodermis walls, thus they must move through the cell membranes via symplasts or apoplasts (small holes)
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9
Q

Describe mycorrhizae

A
  • Symbiotic relation between plants and fungus colonising root cortex
  • Plants give carbs to fungi
  • Plants receive inorganic fuel materials
  • Fungal networks increase volume of soil from which roots can obtain nutrients
  • Fungi secrete enzymes that make soil nutrients more available
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10
Q

Endomycorrhizae vs Ectomycorrhizae

A
  • Endomycorrhizae:
    Fungal networks within root cells
    Enhance plants uptake of PHOSPHORUS
  • Ectomycorrhizae:
    Thick sheath of fungal cells and filaments that surround root tip
    Provide plants with NITROGEN
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11
Q

Describe rhizobia

A
  • N2 needs to be converted to ammonia
  • Plant mutualism with bacteria gain access to nitrogen
    1. Nitrogen-fixing bacteria x outside of root then enter root hair or break in epidermis
    2. The bacteria take up residence in a root nodule formed by dividing root cells
  • Rhizobium → N to plant → N incorporated into seeds → plant protein
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12
Q

Describe Bryophytes

A
  • Can be haploid or diploid
  • Sperm disperses through ground water
  • Diploid zygote (fertilised egg) is retained within female reproductive organ
  • Mosses, Liverworts, Hornworts
  • Non-vascular plants
  • Haploid gametophyte is the dominant generation
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13
Q

What is the sporophyte phase within plants?

A
  • Asexual phase
  • Diploid (two sets of chromosomes)
  • (Bryohphyte) Grows a shoot, like a leaf where it creates a capsule that buds at the top of female gametophyte and within itself meiosis takes place, cutting the chromosome # in ½ and releasing haploid spores to the environment. These will germinate and grow into new plants, cycle repeats
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14
Q

Describe the gametophyte phase

A
  • Sexual phase
  • (Bryohphyte) There are male and female gametophytes, males produce sperm which are released via rain and fertilise women eggs, both via mitosis. Then the egg is coated and becomes an embryo which grows into a sporophyte. This is like the impregnation and child growth phase
  • The diploid sporophyte results from the fusion of two gametes.
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15
Q

What is sporopollen?

A

Protects spores from UV radiation and desiccation as they move through the air, is present in all land plants

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16
Q

What are the major trends of land plant evolution?

A
  • Decrease in size
  • Increase in gametophyte independence generation (gametes get smaller)
  • Increased prominence of sporophyte generation (sporos getting larger)
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17
Q

What are the two types of seed plant?

A
  • Angiosperms: Flowering
  • Gymnosperms: Conifers
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18
Q

What are the 4 major steps of the plant life cycle?

A
  1. Formation of two types of spores
  2. A) Spores undergo mitosis inside sporangia, single haploid → female gametophyte
    B) Spores undergo meiosis inside sporangia, large # of haploids → male gametophyte
  3. Pollination
  4. Maturation of fertilised ovule into seed
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19
Q

How do seeds get produced in gymnosperms?

A
  1. Female gametophyte develops in ovule cone, male gametophytes develop in pollen cones
  2. Males produce pollen, which are released an land in the female ovule cones
  3. Pollen germinates and the pollen tube grows towards the female gametophyte
  4. Fertilized ovule becomes seed, gets released and germinates in the ground, cycle repeats
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20
Q

What is an ovule cone?

A

Found in upper branches of gymnosperms, produce spores that develop into female gametophytes

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21
Q

What is the embryo of a seed?

A

Centre of the seed that develops from zygote, fusion of gametes from two different plants and will become next sporophyte generation

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22
Q

What do seeds store and how is it beneficial?

A

Seeds store food within the sporopellen walls. This is beneficial because when dispersed they have a nutrient source which increases their chance of germination during the vulnerable time

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23
Q

The gametes of _____ are spread by wind and the gametes of ____ are spread by rain

A

seed plants, spore plants

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24
Q

What’re the two outer and inner organs of angiosperms?

A

Outer:
- Petals
- Sepals (green base)
Inner:
- Stamen
- Carpals

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25
Q

How do ovules develop in angiosperms?

A
  1. In the ovary there are sporangium which posses a single diploid cell that undergoes meiosis resulting in four haploid cells (spore formation)
  2. One of the haploid spores develop into a female gametophyte that fills the sporagnium (gametophyte development)
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26
Q

In angiosperms ____ are the female reproductive organs and _____ are the male ones

A

Carpals, Stamen

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27
Q

How does pollen development work in angiosperms?

A
  1. Begins in anther, has 2-4 sporangia
  2. Diploid cells in sporangia undergo meiosis and result in haploid spores
  3. Haploid spores become male gametophyte cells surrounded by sporopollenin
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28
Q

What is unique bout double fertilisation?

A

In double fertilisation one sperm from male gamet. fertlises and forms a zygote, the other one forms a triploid (3n) cell. The two combine and the zygote is the embryo and the 3n acts as the endosperm

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29
Q

What is apoximis?

A

The process of asexually developing a seed without fertilisation

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30
Q

Describe the shoot apical meristem

A
  • Maintains a constant size even though it is the site of rapid cell division
  • As cells become further away from the tip, they cease to divide
  • Meristem identity genes are expressed near the shoot tip so cells can maintain ability to divide
  • Zone of cell elongation located just beneath shoot apical meristem
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31
Q

In seed plants where do branches grow from?

A

Auxillary buds

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32
Q

Leaves begin as small bumps, the ___ ___. Elongating cells within a developing leaf form discrete strands of _____ ____ which give rise to xylem and phloem within leaf veins and _____ (leaf stem) attaching the leaf to the stem

A

leaf primordia, procambial cells, petiole

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33
Q

What triggers flower growth and where?

A

The presence of the protein florigen turns a shoot apical meristem into a flowering meristem

34
Q

What are the different hormones of plants and their functions?

A
  • Auxin: Causes shoots to elongate, determines where new leaves will form, connects new leaves to xylem and phloem, controls directionality of growth
  • Gibberellic acid: Control internode elongation by reducing force needed for plant cell walls to expand. Stimulate cell division and elongation, break seed dormancy, and speed germination
  • Cytokinins: Control internode elongation by reducing force needed for plant cell walls to expand. Stimulates growth of branches from axillary buds BUT suppressed in growing shoots by auxin and strigolactone. If apical meristem is damaged, cytokinin synthesis increases and triggers growth of axillary buds
  • Ethylene: It induces ripening, causes leaves to droop (epinasty) and drop (abscission), and promotes senescence. Plants often increase ethylene production in response to stress, and ethylene often is found in high concentrations within cells at the end of a plant’s life
  • Abscisic acid: A general plant-growth inhibitor. It induces dormancy and prevents seeds from germinating; causes abscission of leaves, fruits, and flowers; and causes stomata to close
35
Q

Why do plants need to grow in diamter?

A
  • To strengthen and support the stem
  • Increase the capacity of vascular system
36
Q

What are lateral meristems?

A
  • Form along the length of stems after elongation is complete
  • Grow in diameter, not in length
  • Become larger over time to accommodate thickness of stem
37
Q

Describe vascular cambium

A
  • Derived from procambial cells within vascular bundle and parenchymal cells between bundles
    Both cells become meristematic
  • Produces cells on both sides:
    - Inside: secondary xylem (wood)
    - Outside: secondary phloem
38
Q

Describe cork cambium

A
  • Renews and maintains outer layer that protects stem from herbivory, mechanical damage, desiccation, and fire
  • Maintains a protective layer around a stem that is actively increasing in diameter
  • Forms from cortex cells that regress to earlier state as meristem cells
39
Q

______ transports water from roots to shoots (active xylem), becomes nonfunctional after several years
_______ no longer transports water; provides mechanical support, nutrient storage; contains resin so it is more resistant to decay and darker

A

Sapwood, Heartwood

40
Q
  • The cork forms a waxy layer of nonliving cells coated with ________ which impedes the diffusion of oxygen
  • _______ are regions of loosely packed cells in the cork that allow oxygen to diffuse into the stem
A

suberin, Lenticels

41
Q

What is the role of tracheids in gymnosperm?

A
  1. Provide structural support
  2. Transport water and nutrients from roots
42
Q

What is the difference between vessels and tracheids

A

Vessels are only present in angiosperms, they are wider and allow for a higher flow rate.

43
Q

How do roots elongate?

A
  • Roots have a root apical meristem where cell devision occurs
  • They have a root cap that protects the meristem and is lost as the root grows
  • Phloem transports auxin from shoot to root
  • Auxin triggers formation of procambial cells which form new xylem and phloem
44
Q

What is a pericycle?

A
  • A single layer of cells just inside the endodermis from which new root meristems develop
  • Extensive branching in roots increases surface area for roots to obtain water and nutrients
45
Q

How does phototropism work?

A
  • Plants absorb blue light
  • Blue light affects placement of PIN proteins
  • Auxin is pumped into the shaded section of a stem, causing the stem to only grow in that area and grow towards the sun
  • High auxin concentrations decrease the rate of cell elongation in roots (trigger production of ethylene)
46
Q

How do plants detect gravity?

A
  • Plants store carbohydrates as starch
  • Starch is large and has a density greater than water (sink to bottom)
  • Organelles pressing on cytoskeleton or membranes causes auxin to move to lower side of plant
  • In the root cap, specialised gravity sensing cells contain large starch filled organelles known as statoliths
47
Q

What type of light triggers germination?

A

Red light, and far-red light inhibits it

48
Q

What is a phytochrome?

A

A photoreceptor that switches between stable forms. In Pf it is inactive, until hit by red light which converts it to Pfr which is active, until hit by far-red light which converts it back to Pf

49
Q

What happens to roots during a drought?

A
  • Root cap cells detect the drought and release abscisic acid (ABA)
  • Stomata close (avoid water vapour loss)
  • The ABA suppresses ethylene
    (ethylene slows root
    elongation by influencing
    orientation of cellulose in cell
    wall, expanding in diameter
    rather than length)
50
Q

_______ is the effect of day length on flowering

A

Photoperiodism

51
Q

Day length is sensed by leaves , the protein ______ is synthesised in leaves and transported via phloem to shoot apical meristem which convert to floral meristems

A

florigen

52
Q

______ is a prolonged period of exposure to cold temperatures, it is necessary for some plants to flower

A

Vernalization

53
Q

_____ are a normally toxic steroid compound that monarch butterfly caterpillars can consume and _____ in parts of their body, which then makes them _____

A

Cardenolides, sequester, toxic to predators

54
Q

The fact that plants are known to produce approximately 6000 different _____ and over 10,000 _____, and the fact that the _____ constitute one of the largest gene families in plants all suggest that as plants evolve defenses, herbivores and pathogens co-evolve to overcome those defenses in an evolutionary “arms race.”

A

alkaloid substances; terpenoid compounds; R genes

55
Q

How can pathogens enter cells ?

A
  • Epidermis is first line of defence – thick walls and waxy cuticle
  • Stomata serve as natural entry point for bacteria, oomycetes, and fungi to gain access to leaves
  • Parasitic plants and some fungi can secrete enzymes to weaken epidermal cell walls
  • Some bacteria and fungi secrete chemicals to prevent stomatal closure
  • Viruses move between cells via plasmodesmata
  • Fungi and bacteria move through xylem
  • Viruses and bacteria move through phloem
56
Q

What is the difference between biotrophic and necrotrophic pathogens?

A

Biotrophic pathogens obtain resources from living hosts, whereas necrotrophic pathogens first kill the cells before exploiting/conolonising

57
Q

What is the difference between virulent and antivirulent pathogens?

A

Virulent pathogens overthrow the host and lead to disease, whereas antivirulent pathogens damage only a small part of the plant and the host contains the infection

58
Q

What is the difference between holoparasitism and hemiparasitism?

A

Holoparasites rely on the host for all of its resources whereas hemiparasites just usurp resources from host xylem but don’t establish their own roots

59
Q

What are the two components of plant immune systems?

A
  1. Basal resistance consists of receptors located on the plasma membrane; recognize highly conserved molecules such as flagellins (present in bacterial flagella) or chitin (in fungal cell walls)
  2. Specific resistance consists of R proteins located inside the cell; expressed by different genes collectively called R genes
60
Q

How do plants protect themselves after detection?

A
  1. Reinforce natural barriers like cell walls, close stomata, and plug xylem
  2. Produce antimicrobial compounds (e.g. attack bacterial or fungal cell walls)
  3. Hypersensitive response where uninfected cells surrounding infection rapidly produce large numbers of reactive oxygen species (ROS)
61
Q

What is the role of reactive oxygen species (ROS)?

A

ROS trigger cell wall reinforcement and cause cells to die, creating a barrier of dead tissue to prevent spread of biotrophic pathogens.

Think of how control burns create a barrier to prevent wildfire spreads. Same idea

62
Q

What is system acquired resistance?

A

If one part of a plant (leaf) is infected, the whole plant develops an immunity to the infection, not just the affected area(s). Requires salicylic acid

63
Q

What is the process of viral infection and resistance in plants?

A
  1. Viral ssRNA is injected into plant genome
  2. It replicates and becomes dsRNA
  3. The dsRNA is identified as foreign and gets cleaved into siRNA
  4. siRNA binds to plant protein complex and retains only one RNA strand
  5. ssRNA destroy siRNA
64
Q

What is the process of crown gal disease?

A
  1. Bacteria enters cell through a wound
  2. Bacterial Ti plasmid is injected into plant genome
  3. Ti genes cause host cells to divide at unprecedented rates, which form a tumor
65
Q

What does Rhizobium radiobacter do?

A

Alters the growth and metabolism of infected cells by inserting some of it’s own genes into the chromosomal DNA of the host plant

66
Q

_________ defences are always expressed. _________ defences are activated upon detection of a threat

A

Constitutive, Inducible

67
Q

What helps alert predators of herbivore presence on plants?

A

Herbivory-induced plant volatiles (HIPV)

68
Q

What does jasmonic acid do?

A

It is a plant stress-hormone which (broadly) enacts varieties of defence mechanisms

69
Q

*Fatty acid-amino acid conjugates (FACs) help with ______ and ______
*Induced defense responses are accompanied by
large-scale ________ re-organization

A

signalling, defence, transcriptional

70
Q

What is the “escape and radiate” hypothesis?

A

A burst of diversification following evolution of a key innovation that allows plants to avoid being eaten

71
Q

What is the Janzen-Connell hypothesis?

A

Similarly related plants are more susceptible to pathogens. So rare seedlings are more likely to live on because of their unrelatedness to their siblings

72
Q

Plants alternate between two multicellular forms:
1. A _____ ______ gen that makes gametes
2. A ______ ______ gen that makes spores

A

haploid gametophyte, diploid sporophyte

73
Q

What’re the benefits of the diploid sporophyte generation?

A
  • Upwards extension to increase dispersal of offspring in air during sporophyte generation
  • Release swimming sperm into surface moisture layers during gametophyte generation
74
Q
  • ______ transports water and dissolved nutrients
  • ______ transports carbohydrates produced by photosynthesis
A

Xylem, Phloem

75
Q

How was pollen evolved?

A
  • Fertilisation no longer required surface moisture
  • Gametophyte generation became retained within tissues of much larger and more productive sporophytes
  • Male gametophytes were packaged into small structures called pollen which travel through air to deliver sperm to female reproductive organs
76
Q

Why were seeds evolved?

A

To increase the probability of next sporophyte generation successfully establishing as free-living plant

77
Q

What’re some defining characteristics of Bryophytes?

A
  • Leafy structures are different from vascular leaves
  • Several cells thick and lack internal air spaces
  • No roots or xylem
  • Anchored by hair-like structures that are a single-cell wide
  • Absorb moisture from rain or dew droplets on surface or pulled by surface tension between stalks/leafy structures
78
Q

What are some traits of pete moss?

A
  • Create wet and acidic conditions that slow decomposition rate
  • Specialized cells that hold onto water and secrete protons
  • Produce phenols to slow decomposition under waterlogged conditions
79
Q

________ (as well as ferns and horsetails) disperse by spores and rely on swimming sperm for fertilization. The most distinctive of them are ______

A

Lycophytes, quillworts (genus Isoetes)

80
Q

What are the 4 evolutionary innovations that contributed to diversification of angiosperms?

A
  • Flowers: brightly coloured petals, fragrant scents, nectar rewards
  • Double fertilization: one fertilization for embryo, another for endosperm
  • Fruits: maturation of ovary containing seed to improve dispersal
  • Vessels: higher rate of water transport than tracheids
81
Q

What are some defining traits of eudicots?

A
  • Need to rebuild stems year after year with minimal investment
  • Annuals complete life cycle within a year
  • Most parasitic and all carnivorous plants are eudicots
    E.g Water-storing cacti, woody shrubs, epiphytes, vines
82
Q

*______ plants, like Maryland Mammoth, flower only when day length is less than a critical value
*______ plants, like radish, lettuce, and some varieties of wheat, only flower when light period exceeds a certain length
*______ plants flower independent of change in day length

A

Short-day, Long-day, Day-neutral

Sem 2 (5 decks)

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