Biology 2.3

Question 1

Ground tissue

Answer 1

structural support and makes up plant mass, consists of parenchyma, collenchyma and sclerenchyma

Question 2

Parenchyma

Answer 2

site of photosynthesis with thin cell walls

Question 3

collenchyma

Answer 3

thicker cell wall provides mechanical support while being flexible

Question 4

sclerenchyma

Answer 4

thickest cell wall for mechanical support

Question 5

dermal tissue

Answer 5

outer layer of plant to prevent dehydration, consists of epidermal layer and guard cells. Also, specialized cells such as root hair cells, stinging cells and glandular cells are also present in this tissue type

Question 6

epidermal layer

Answer 6

epidermal cells secrete a waxy cuticle to prevent desiccation (drying out)

Question 7

guard cells

Answer 7

specialized cells on epidermal layer which surround openings on leaf structure called stomata

Question 8

Vascular tissue

Answer 8

allows for transport of water and nutrients throughout the plants, only found in tracheophyte plants, consists of vascular bundles xylem and phloem

Question 9

Xylem

Answer 9

Part of vascular bundle in vascular tissue, transports water and minerals from roots to leaves and acts as mechanical support, contains non-continuous secondary cell wall for added mechanical strength and gaps between these walls are called pits, at maturity of xylem tissue the cells are dead and do not contain any cellular components, two types of xylem cells are tracheids and vessel elements

Question 10

tracheids

Answer 10

type of xylem cell in vascular bundle in vascular tissue, it is long tapered cells, water passes from one to another through pits at overlapping tapered of the cell

Question 11

vessel elements

Answer 11

type of xylem cell in vascular bundle in vascular tissue, it is shorter and wider than tracheids with less or no taper at cell ends. Column of vessel elements is called a vessel. Water passes from one vessel to another through perforations which are holes between cells devoid of both primary and secondary cell walls

Question 12

Phloem

Answer 12

Part of vascular bundle in vascular tissue, transports sugars from leaves to roots, made up of sieve-tube members cells that form fluid-conducting columns called sieve tubes. Pores at end of these cells form junctions that connect cellular cytoplasm of neighbouring cells called sieve plates. Sieve-tube members live at maturity although they lack nuclei and ribosomes. For metabolic needs, each sieve-tube member is connected to a companion cell (parenchyma) that contains organelles via a tube called plasmodesmata

Question 13

Leaf structure

Answer 13

consists of upper epidermis, palisade mesophyll, spongy mesophyll, vascular bundles and lower epidermis

Question 14

Upper epidermis

Answer 14

part of leaf structure, uppermost layer, covered by the cuticle (which is composed of cutin) which reduces transpiration, specialized epidermal cells may have hair-like structures called trichomes of various function

Question 15

palisade mesophyll

Answer 15

part of leaf structure, second layer, contains parenchymal cells and chloroplasts for photosynthesis

Question 16

spongy mesophyll

Answer 16

part of leaf structure, second lowermost layer, parenchyma cells more loose, has air chambers to provide CO2 to photosynthesizing cells and O2 to respiring cells

Question 17

vascular bundles

Answer 17

part of leaf structure, dispersed throughout spongy mesophyll, composed of xylem and phloem tissue, mesophyll cells called bundle sheath cells surround the vascular bundles so its tissues is not exposed to intercellular spaces. Bundle sheath cells also provide the anaerobic environment in C4 plants to fix CO2

Question 18

lower epidermis

Answer 18

part of leaf structure, lowermost layer, covered by cuticle and has stomata which is small opening surrounded by guard cells at underside of leaf, if stomata is closed then CO2 is not available and no photosynthesis, if stomata is open then CO2 enters but plant risks desiccation from excessive transpiration. Each stomata is surrounded by two guard cells which are controlled by water:
- open stomata: water diffuses into guard cell to cause expansion and thinner portion of cell wall bulges out to open stomata, occurs with low concentration of CO2 in leaf
- close stomata: water diffuses out of guard cell which closes the stomata, occurs at high temperature to prevent water loss.
Generally, stomata opens during the day to get CO2 for photosynthesis and closes at night because CO2 accumulates at night due to lack of light for photosynthesis and occurrence of respiration

Question 19

Root structure

Answer 19

absorb water and nutrients for photosynthesis, has a few layers, consists of epidermis, cortex, endodermis, casparian strip, vascular cylinder (stele)

Question 20

epidermis

Answer 20

part of root structure, outside surface and has root hairs in zone of maturation to increase absorption, constant root growth required because root hair dies as zone of maturation ages

Question 21

cortex

Answer 21

part of root structure, makes up bulk of root, stores starch

Question 22

Endodermis

Answer 22

part of root structure, single layer of cells under cortex to regulate water movement in roots

Question 23

casparian strip

Answer 23

part of root structure, band of fatty material between endodermis cells called Suberin that creates water impermeable layer between cells. Water passes through endodermal cells which controls water to centre of root and prevents backwards movement

Question 24

vascular cylinder (stele)

Answer 24

part of root structure, tissues inside endodermis that can be arranged in different ways, contains pericycle which is layer between phloem and endodermis from which lateral roots arise. Pericycle contains the vascular tissue.

Question 25

Stem structure

Answer 25

casparian strip and endodermis usually missing, consists of epidermis, cortex and vascular cylinder

Question 26

Epidermis

Answer 26

part of stem structure, outer layer with epidermal cells covered in waxy cutin substance which forms the cuticle, has guard cells around stomata, may have stinging cells that are specialized trichomes which may inject irritable substances when touched

Question 27

cortex

Answer 27

part of stem structure, under epidermis, stores carbohydrates, composed of ground tissue (parenchymal cells), bulk of stem between epidermis and vascular cylinder

Question 28

Vascular cylinder

Answer 28

part of stem structure, has vascular bundle (xylem and phloem) and pith which is spongy parenchyma cells that store and transport nutrients. Single layer between xylem and phloem may remain undifferentiated, later becoming vascular cambium

Question 29

Flower structure - angiosperms

Answer 29

anthophyta is group of plantae organisms that flower and produce seeds in enclosed fruits. Consists of receptacle, sepal, petal, pistil and stamen

Question 30

receptacle

Answer 30

part of angiosperm flower structure, connects flower to stem

Question 31

sepal

Answer 31

part of angiosperm flower structure, encloses flower bud before flowering

Question 32

petal

Answer 32

part of angiosperm flower structure, attracts pollinators

Question 33

pistil

Answer 33

part of angiosperm flower structure, female reproductive structure, consists of: - ovary: swollen base of pistil has gametophyte (eggs) which develop into seeds - style: stalk tissue connecting ovary and stigma - stigma: top of pistil that is sticky and pollen sticks

Question 34

Stamen

Answer 34

part of angiosperm flower structure, male reproductive structure, consists of: - anther: at tip of stamen with sac-like structures called microsporangia that produce pollen - filament: stalk tissue connecting anther to flower. At stamen base, food nectaries reward pollinators

Question 35

before angiosperm fertilization

Answer 35

The megaspore mother cell within the ovule divides by meiosis to make 4 haploid megaspore cells, one of which undergoes 3 mitotic divisions to make 8 nuclei. 6 of which undergo cytokinesis. Result is a polar embryo sac that has a small opening called the micropyle at one end where there is an egg cell and 2 synergid cells. At the opposite end, there are 3 antipodal cells and in between the two ends are 2 haploid polar nuclei.

Question 36

angiosperm fertilization

Answer 36

Pollinators or wind allow pollen to land from anthers to stigma. Pollen becomes elongating cell called pollen tube that has 2 sperm cells and grows through the style down to the ovule. Pollen tube enters embryo sac through micropyle where one sperm fertilizes the egg to make diploid zygote. Second sperm cell fuses with polar nuclei to make a triploid nucleus that divides by mitosis to make endosperm that gives nourishment to embryo and for seed development. This process of fertilization of the egg and polar nuclei is called double fertilization

Question 37

Seed structure

Answer 37

coniferophyta (gymnosperms) and anthophyta (angiosperms) are both seed plants. Angiosperms can be dicots which contain 2 inner seed leaves or monocots which contain 1 inner seed lead. Consists of seed coat, storage material and embryo

Question 38

Seed coat

Answer 38

Part of seed structure. Outer covering of seed, prevents embryo from drying out

Question 39

Storage material

Answer 39

Part of seed structure. Can consist of endosperm or cotyledon depending on stage. Endosperm produced from double fertilization gives nourishment to inner seed leaves called cotyledons. Transfer of storage material from endosperm to cotyledons causes endosperm to be depleted and cotyledons enriched in carbohydrates

Question 40

Embryo

Answer 40

Part of seed structure. Consists of epicotyl (eventually becomes shoot tip), plumule (is young leaves attached to epicotyl), hypocotyl (structure below epicotyl that is attached tot he cotyledons and eventually becomes young shoot), radicle (found in some plants and develops into the root) and coleoptile (sheath that surrounds and protects the epicotyl)

Question 41

Germination and growth step 1/5

Answer 41

Seeds become dormant after reaching maturity until cues (water, temperature, light) are triggered

Question 42

Germination and growth step 2/5

Answer 42

Germination begins with water absorption, causing seed to swell, seed coat cracks

Question 43

Germination and growth step 3/5

Answer 43

Radicle produces roots and root caps at the end protect the apical meristem

Question 44

Germination and growth step 4/5

Answer 44

Hypocotyl elongates to produce the shoot

Question 45

Germination and growth step 5/5

Answer 45

Seed undergoes primary growth where it grows at apical meristem tissue found at tips of roots and shoots

Question 46

Primary growth

Answer 46

Increase in length of root or shoot of plant, occurs for monocots at the apical meristems. Consists of zone of cell division, zone of elongation, and zone of maturation/differentiation

Question 47

Zone of cell division

Answer 47

Where meristematic cells are rapidly undergoing division

Question 48

Zone of elongation

Answer 48

The zone of cell division can develop into this zone where the newly formed cells absorb water and elongate

Question 49

Zone of maturation/differentiation

Answer 49

once the cells elongate, they become specific types of primary plant tissue such as vascular tissue, parenchyma or epidermal cells

Question 50

Secondary Growth

Answer 50

Increase in lateral dimensions or girth of the plant. Occurs in conifers and woody dicots, in addition to primary growth. Occurs at the 2 primary meristems: - vascular cambium: produces secondary xylem and phloem - cork cambium: produces periderm which is the outer protective covering

Question 51

Transport of water

Answer 51

when water and minerals enter root hairs via osmosis, it moves to the centre of the root in one of two ways: - apoplastic: movement through cell walls, the "non living" portions - symplastic: movement though cells through cytoplasm via connecting plasmodesmata When water reaches endodermis, it can only enter vascular cylinder through symplast pathway because apoplast pathway is blocked by casparian strips. Endodermis is selective to what can enter the plant, K+ can enter but not Na+.

Question 52

Osmosis

Answer 52

Concentration gradient between soil (low) and inside the root (high) allows for water to move into the root. There is high concentration of solutes in the root because water goes from root to xylem, leaving behind a buildup of minerals that cannot pass. Movement of water into root helps push water up the xylem via osmotic force called root pressure, however, this is minimal. At low level of transpiration but high root pressure, water droplets may be secreted on plant surface, called guttation.

Question 53

Capillary action

Answer 53

attractive adhesive property between water and xylem allows water to go up the xylem without meniscus forming

Question 54

Cohesion-tension theory

Answer 54

at warm temperatures from the sun, water transpires (AKA evaporates) from leaves of the plants which causes negative pressure to build up at the leaves. Water is cohesive, water molecules attracted to each water. Cohesive property causes water to move up the plant in a single column because it is pulled by transpiration. This process is called bulk flow

Question 55

Plant hormones

Answer 55

Auxin, gibberellins, cytokinins, ethylene, abscisic acid

Question 56

Auxin (IAA)

Answer 56

promotes plant growth via elongation of developing cells. Asymmetrical distribution of IAA can cause asymmetric growth. Phototropism: portion of plant with less sunlight will release IAA, causing the shaded side to grow faster, results in plant bending towards sunlight as a result

Question 57

Gibberellins

Answer 57

promotes cell growth and fruit development seed germination. High concentration can cause bolting or rapid increase of length by stems.

Question 58

Cytokinins

Answer 58

stimulates cell division, influences organ development and determines whether roots/shoots will develop, delays aging of leaves and are often added to prolong the plant's usefulness

Question 59

ethylene

Answer 59

Gas that promotes fruit ripening and stimulating flower production, influences leaf abscission which is the aging and dropping of leaves

Question 60

Abscisic Acid (ABA)

Answer 60

growth inhibitor that can maintain dormancy in seeds