EXAM 3

Question 1

How do plants enable other life forms to survive on land

Answer 1

they supply oxygen and they are a key food source for terrestrial animals. They also physically create habitats

Question 2

what is the closest relative of plants

Answer 2

green algae (charophytes)

Question 3

Traits shared with various algal groups

Answer 3

multicellular eukaryotes, photosynthetic autotrophs, chloroplast structures containing chlorophyll a and b. cell walls of cellulose

Question 4

Traits shared with only charophytes

Answer 4

plasma membrane protein structure, structure of sperm flagella (if present), sequence similarities in nuclear, chloroplast, and mitochondrial DNA, Sporopollenin polymer (polymer that presents charophyte zygotes from drying out, plant spore walls)

Question 5

Traits unique to plants (derived traits: what makes a plant a plant)

Answer 5

1. Alternation of generations:
   2 multicellular life stages, Haploid stage (n): spore (produced by meiosis), gametophyte, gametes: egg, sperm (produced by mitosis); Diploid stage (2n): zygote, embryo, sporophyte
2. Walled spores produced in sporangia:
   Sporophyte produces spores in sporangia, spore walls contain sporopollenin, which makes them resistant to harsh environments
3. Apical Meristems:
   localized regions of cell division at the tips of roots and shoots (apical meristems), these cells divide continuously, enabling elongation of roots and shoots for better resource acquisition
4. the cuticle (waxy covering of the epidermis that reduces water loss)
5. the stomata (pores that facilitate gas exchange between the outside air and internal plant tissues)

Question 6

sporopollenin

Answer 6

in charophytes a layer of durable polymer that prevents exposed zygotes from drying out. Similar chemical adaptation is found in the tough sporopollenin walls that encase plant spores

Question 7

what benefits were offered by a terrestrial above the waterline

Answer 7

sunlight not being filtered by water and phytoplankton; atmosphere with more plentiful carbon dioxide than water; soil by the water was rich in some mineral nutrients

Question 8

what challenges did a terrestrial habitat above the waterline bring

Answer 8

scarcity of water and a lack of structural support against gravity. Early plants lacked true roots making absorption of nutrients from soil challenging. fossils suggest that symbiotic associations with fungi (mycorrhizae) may have helped plants without roots colonize land.

Question 9

what do “nonvascular” plants lack

Answer 9

an extensive transport system. All nonvascular plants- liverworts, mosses, and hornwarts- are informally called byrophytes. Bryophytes are not a monophyletic group (clade)

Question 10

what does vascular tissue do in vascular plants

Answer 10

vascular tissues are cells joined to tubes for the transport of water and nutrients. Plants that have a complex vascular tissue system are called vascular plants

Question 11

order of evolution to produce the vast diversity of plants on earth today

Answer 11

vascular tissue —> seeds ——> flowers

Question 12

Vascular plants are divided into what 2 clades

Answer 12

lycophytes: club mosses and their relatives
monilophytes: ferns and their relatives

Question 13

seedless vascular plants

Answer 13

have an extensive vascular transport system, but do not produce seeds. they are composed of two clade but DO NOT form a clade

Question 14

third clade of vascular plants: seed plants

Answer 14

vascular plants that produce seeds. a seed is an embryo packaged with a supply of nutrients inside a protective coat.

Question 15

what 2 groups can seed plants be divided into

Answer 15

gymnosperms: from a clade that produce seeds that are not enclosed in chambers (“naked seeds”)
angiosperms: from a clade that produce seeds that develop inside chambers that originate within flowers
nearly 90% of living plant species are angiosperms

Question 16

Major steps in evolution of land plants

Answer 16

Protection from desiccation: waxy cuticle/stomates, protected males and female gametophyte generation
Overcoming ‘split’ world: vascular tissue
Pollen: independence from water for reproduction
Seeds: dormant propagules with energy source
Flowers: Maximizing reproductive efficiency

Question 17

Why are seeds and pollen grains key adaptations for life on land

Answer 17

all seed plants have reduced gametophytes, heterospory, ovules, and pollen. These adaptations help plants cope with drought and exposure to UV radiation. Water is not required for fertilization in seed plants

Question 18

Mosses and other bryophytes have life cycles dominated by _________, whereas ferns and other vascular plants have _________- dominated life cycles

Answer 18

gametophytes, sporophyte

Question 19

at some point, seed plants and their ancestors became heterosporous producing what 2 kinds of spores

Answer 19

Megasporangia: on modified leaves called megasporophylls produce megaspores that give rise to female gametophytes
Microsporangia: on modified leaves called microsporophylls produce microspores that give rise to male gametophytes.
Each megasporangium has one megaspore, whereas each microsporangium has many micropspores

Question 20

what does the integument do

Answer 20

a layer of sporophyte tissue that evelops and protects the megasporangium. Gymnosperm megasporangia are surrounded by one integument, whereas those in angiosperm usually have 2 integuements.

Question 21

what is an ovule

Answer 21

The whole structure- megasporangium, megaspore, and their integument(s)- is called an ovule. Inside each ovule, a female gametophyte develops from a megaspore and produces one or more eggs. Structure that contains and protects the female gametophyte. “parasitic” on sporophyte tissue.

Question 22

pollen

Answer 22

structure that contains and protects the male gametophyte. Moves by wind or animals, allows independence from water and flagellated sperm. (contains entire male gametophyte including the sperm cell)

Question 23

seed

Answer 23

an embryo, with a food supply, packaged in a protective coat

Question 24

pollination

Answer 24

the transfer of pollen to the part of a seed plant that contains the ovules. If a pollen grain germinates, it gives rise to a pollen tube that discharges sperm into the female gametophyte within the female ovule

Question 25

advantages of reduced gametophytes

Answer 25

Seed plant life cycles are sporophyte-dominated; gametophytes are microscopic and dependent
Gametophytes develop from spores retained within the sporangia of the sporophyte
They are protected from environmental stress and receive nutrients from the parent sporophyte

Question 26

heterospory: the rule among seed plants

Answer 26

Homosporous plants produce one kind of spore and generally have bisexual gametophytes
Heterosporous plants produce two types of spores, which form either male or female gametophytes
Ferns and other close relatives of seed plants are homosporous; seed plants are heterosporous
Spores develop within sporangia born on modified leaves called sporophylls:
- megasporophylls bear megasporangia that produce megaspores, which produce female gametophytes
- microsporophylls bear microsporangia that produce microspores, which form male gametophytes

Question 27

Evolutionary advantage of seeds

Answer 27

When the sperm fertilizes the egg of a seed plant, the zygote grows into a sporophyte embryo
The ovule develops into a seed
Seeds can disperse over long distances by wind or other means
Both seeds and spores provide protection from harsh conditions and facilitate dispersal BUT seeds provide evolutionary advantages over spores: multicellular (spores are single cells), can remain dormant for years until conditions are favorable for germination (spores shorter-lived), stored food to nourish and grow seedlings (spores don’t provide nourishment to gametophytes), seeds can be transported longer distances (spores usually drop close to present plant)

Question 28

how does structure fit function in vascular plants

Answer 28

natural selection has molded plant structure to support function at the organ, tissue, and cellular level.
At the organ level: leaves provide surface area, stems support and elevate, roots anchor and absorb
At the tissue level: dermal tissue protects organs, vascular tissue supports and transports, ground tissue carries out photosynthesis
At the cellular level: photosynthetic cells contain chloroplasts, tube shaped cells transport resources, cells with root hairs increase surface area

Question 29

what are the 3 vascular plant organs

Answer 29

roots, stems, and leaves. These organs form the root system and the shoot system

Question 30

what are the primary functions of roots

Answer 30

anchoring the plant, absorbing mineral and water, storing carbohydrates. Primary root is the first to emerge from the seed and lateral roots branch off to improve anchorage and water abosrption

Question 31

what is a taproot

Answer 31

it is one main vertical root that usually develops from the primary root. Taproots enable plants to grow taller and gain access to more favorable light conditions and sometimes provide an advantage for seed and and pollen dispersal. It can also be specialized for food storage. Usually energetically expensive to make

Question 32

what is a fibrous root system

Answer 32

a thick mat of slender roots spreading out below the soil surface. The primary root dies early and many small roots emerge from the stem. These roots are adventitious. Each root forms its own lateral roots who form their own lateral roots, the fibrous root system is good at preventing soil erosion.

Question 33

what is a stem

Answer 33

a stem is a plant organ bearing leaves and buds. Stems consist of an alternating system of nodes and internodes. The primary function of the stem is to maximize photosynthesis.
Nodes are the points where leaves are attached and internodes and the stem segments between nodes
Apical bud is where most growing occurs, axillary bud has the potential to form a lateral branch, thorn, or flower
many plants have modified stems that perform alternate functions (ex: potato is a stem not a root)

Question 34

what is the purpose of a leaf

Answer 34

in most vascular plants, the leaf is the main photosynthetic organ. In addition to intercepting light, leaves exchange gases with the atmosphere, dissipate heat, and defend themselves from herbivores and pathogens.
a leaf consists of flattened blade and a petiole which joins the leaf to the stem. Leaf shape may be simple or compound.
most leaves are specialized for photosynthesis but some plant species have evolved modified leaves that serve additional functions

Question 35

what are the three fundamental plant tissue types

Answer 35

dermal, vascular and ground
each tissue type forms a tissue system that is continuous throughout the plant. The characteristics of the tissues and their spatial relationships vary in different organs

Question 36

dermal tissue

Answer 36

serves as the outer protective of the plant. In nonwoody plants, it is usually a single tissue called the epidermis. In leaves and most stems the cuticle is a waxy epidermal coating. In woody plants, protective tissues called the periderm replace the epidermis in older regions of stems and roots. 
In shoots, specialized epidermal cells called guard cells are involved in gaseous exchange
Trichomes are another class of highly specialized epidermal cells that are outgrowths found in shoots.

Question 37

vascular tissue

Answer 37

2 major functions are to facilitate transport of materials through plant and to provide mechanical support. There are 2 types of vascular tissue the xylem and the phloem. xylem conducts water and dissovled minerals upward from roots into the shoots. Phloem transports sugars from where they are made to where they are needed/stored.
Stele is the vascular tissue of a root or stem. The organization is variable depending on location.
In angiosperms roots= solid central vascular cylinder. in angiosperm stems and leaves is divided into vascular bundles

Question 38

ground tissue

Answer 38

tissue that is not dermal or vascular. Ground tissue internal to the vascular tissue is pith. Ground tissue outside the vascular tissue is cortex.
ROOT. “middle” layer between epidermis and stele
Ground tissue includes cells specialized for storage, photosynthesis, support, and short distance transport

Question 39

common types of plant cells

Answer 39

plant cells undergo cell differentiation; specialization in structure and function during development. The structural adaptations of various plant cells make their specific functions possible
6 basic types of cells:
Parenchyma: living metabolism and storage (ground to dermal)
Collenchyma: living, flexible support (ground or dermal)
Sclerenchyma: living or dead rigid support (ground or dermal
Xylem: tracheids and vessel elements. dead, water-conducting cells (vascular)
Phloem: sieve tibe element, living, sugar conducting cells (vascular

Question 40

intermediate growth

Answer 40

a plant can grow throughout its life. Continuos growth is possible due to the activity of meristems, undifferentiated tissues composed of dividing cells (stem cells)

Question 41

apical meristems

Answer 41

located at root and shoot tips, provide the cells that enable primary growth (growth in length).
Undifferentiated (stem) cells.
As cells “move down” (tip grows away) they become partially differentiated (primary meristems) that will give rise to 3 tissues. The new cells grow and mature and become functional tissues

Question 42

secondary growth

Answer 42

secondary growth is growth in thickness and it is done through the lateral meristems: vascular cambium and cork cambium. These cylinders of dividing cells extend along the length of the roots and stems.
Vascular cambium: adds vascular tissue called secondary xylem (wood) and secondary phloem
Cork cambium: replaces epidermis with thicker, tougher, periderm that protects the stem from water loss and pathogen invasion.

Question 43

primary growth of roots

Answer 43

entire biomass of a primary root is derived from the root apical meristem. This makes a root cap that protects the apical meristem as it pushes through soil and secretes a polysaccharide slime as lubrication as it pushes through the soil. Growth occurs just behind the tip in 3 overlapping zones: division, elongation, and differentiation or maturation

Question 43

primary growth

Answer 43

primary growth arises from cells produced by apical meristems and elongates roots and shoots. In herbaceous plants, most of the plant consists of primary growth; in woody plants only new, non woody parts represent primary growth

Question 44

protoderm

Answer 44

the outermost primary meristem gives rise to the epidermis. Root hairs are the most prominent feature (function in absorbing water and minerals)

Question 45

ground meristem

Answer 45

in between the protoderm and the procambium, gives rise to mature ground tissue. Consists mostly of parenchyma cells, found in the cortex. Stores carbs and transports water and salts from the root hairs to the center of the root.
Cortex also allows for extracellular diffusion of water, minerals, and oxygen from the root hairs inward.
Innermost layer of the cortex is the endodermis. It forms a boundary with the vascular cylinder. It is a selective barrier that regulates the passage of substances from the soil into the vascular cylinder

Question 46

procambium

Answer 46

gives rise to the vascular cylinder which consists of a solid core of xylem and phloem tissues surrounded by a cellular layer called the pericycle (support and lateral roots).
lateral branch roots arise from the pericycle and destructively push through outer tissues. Branching is a form of primary growth

Question 47

primary growth of shoots

Answer 47

the shoot apical meristem makes three primary meristems: the protoderm, ground meristem, and procambium.
The shoot apical meristem is protected by the leaves of the apical bud.
Axillary buds each have their own apical meristem. Due to plant communication the closer an axillary bud is to an active apical bud, the more inhibited it is ( apical dominance)

Question 48

stem primary growth and anatomy

Answer 48

stem is covered by an epidermis and a waxy cuticle preventing water loss. Some specialized epidermal cells in the stem are guard cells and trichomes
Ground tissue is mostly parenchyma cells but collenchyma cells are just beneath the surface and strengthen the stem during primary growth. Sclernchyma support the parts of the stem that are no longer growing.
vascular tissue of most stems consist of vascular bundles arranged in a ring. The xylem in each bundle faces the pith and the phloem faces the cortex.

Question 49

leaf primary growth and anatomy

Answer 49

leaves develop from leaf primordia; projections that emerge along the sides of teh shoot apical meristem.
Unlike roots and stems, secondary growth in leaves in minor or non existent.
leafs ground tissue is called the mesophyll and it is between the upper and lower epidermal layers. The mesophyll has 2 distinct layers palisade and spongy. Paliside is under the upper epidermis and consists of one or more layers of chloroplast rich cells specialized for light capture. Springy mesophyll is inward the lower epidermis and consists of irregularly shaped cells that have fewer cholorplast
vascular tissue of each leaf is continuous with the vascular tissue of the stem.

Question 50

in woody plants primary and secondary growth occurs ________

Answer 50

simultaneously

Question 51

vascular cambium

Answer 51

a cylinder of meristematic cells wholly responsible for the production of secondary vascular tissue. In a woody stem it is located outside the pith and the primary xylem and to the inside of the primary phloem and the cortex.
As these cells divide they increase the cambiums circumference and add secondary xylem to the inside and secondary phloem to the outside. each ring is larger than the previous ring increasing the diameter of roots and stems

Question 52

development

Answer 52

cells form specialized tissues, organs, and organisms through the process of development.
Developmental plasticity (environmental cues): many aquatic plants produce 2 types of leaves. different leaves are formed depending on whether the shoot apical meristem is submerged or not.
Development is genetic and influenced by the external environment
The 3 overlapping processes involved in the development of a multicellular organism are growth, morphogenesis and cell differentiation.

Question 53

Growth: Cell division

Answer 53

cell division in meristems increases the number of cells. During cytokinesis a cell plate develops that splits the cell into 2 cells (usually symmetrical division). But division is not growth (no change in size) but it creates the opportunity for growth.
Asymmetrical cell division has an impact on development (formations of guard cells involves asymmetrical development.)

Question 54

Growth: Cell expansion

Answer 54

cell elongation/expansion is the process directly responsible for increase in plant size. Expansion rarely happens the same way in all directions. Typically it expands along the plants main axis. HTe orientation of cellulose and microfibrils in the innermost layers of the cell wall causes this differential growth. Microbfibrils don’t stretch so so the cell expands mostly perpendicular to the main orientation of the microfibrils.

Question 55

morphogenesis and pattern formation

Answer 55

pattern formation is the development of specific structures in specific locations. There are 2 hypthiesis to explain how this is determined for a cell.
1: lineage-based mechanisms say that cell fate is determined in early development and passed to daughter cells (“animal model”). The basic pattern of cell differentiation is mapped out according to the directions in which meristemic cells divide and expand.
2:Position-based mechanisms propose that cell fate is determined by final position in an emerging organ.
Root epidermis forms root hairs or hairless cells depenign on the number of cortical cells it is touching (changes expression of controlling gene)

Question 56

shifts in development: phase changes

Answer 56

cells of a developing organism can synthesize different proteins and diverge in structure and function even though they share a common genome.
Juvenile phase turns in to adult vegetative stage some species exhibit conscious changes in leaf shape. Any new leaves that develop on branches that emerge from axillary buds at juvenile nodes will also be juvenile.
Evidence suggests that the activation or inactivation of specific genes involved in cell differentiation results.
flowering formation involves a phase change from vegetative growth to repordcutive growth. This change is triggered by a combo of environmental cues and internal signals (hormones). Flower growth is determinate (vegetative growth is indeterminate)
Production of of a flower by a shoot apical meristem generally stops the primary growth of the short. The transition from negative the flowering frwoth is associated with the switching on of flower inducing genes. The protien products of the genes are transcription factors that regualt the genes required of the indeterminate vegativive meristems to determinate floral meristems.
Induces the growth of 4 whirls of flower organs: speals, petals, stamen (male), and carpel (female)

Question 57

The ABC hypothesis

Answer 57

Three classes of genes direct the formation of the four types of floral organs . Each class of genes is switched on in two specific whorls of the floral meristem.
A genes switched on in 2 outer whorls (sepals and petals). B genes are switched on in the 2 middle whorls (petals and stamen). C gens are switched on in 2 outer whorls (stamens and carpels)
A genes only: sepal arises
A and B genes: petals arise
B and C genes: stames arise
C gens only: carpels arise

Question 58

aquring resources

Answer 58

algal ancestors= abosrbed water, minerals, and CO2 directly from the water.
Early nonvascular land plants lived in shallow water of moist and has short aerial shoots
Colonization of dryer places and competition with neighboring plants led to structures land plants have today

Question 59

plant resources in the air

Answer 59

light and CO2.

Question 60

what does the xylem transport and what does the phloem transport

Answer 60

the xylem transports water and mineral from roots to shoots. The phloem transports products of photosynthesis from where they are made/stored to where they are needed

Question 61

shoot architecture and light capture

Answer 61

stems provide structural support for leaves (primary light capture structure)
shoot length and branching pattern affect light capture; taller and highly branched= more access to sunlight
Due to limited energy trade off between height and branching; the more energy invested into branching, the less energy available for growth in height.
There is a positive correlation between water availability and leaf size. The largest leaves are found in tropical rain forests, where as the smallest are usually found in dry or very cold environments such as deserts.
Phyllotaxy is the arrangement of leaves of on stem. One leaf per node is alternate or spiral. Two leaves per node is opposite. More than 2 leaves per node is whorled. Most angiosperms have alternate phyllotaxy with leaves arranged in the siral at 137.5 angles because that allows for the most light.
Total leaf area is the key factor in photosynthetic efficiency.
Leaf area index (LAI) is the ratio of total upper leaf surface of a plant or crop divided by the surface area of land on which it grows. A value up to 7 is common for many mature crops. If self shading happens the plant begins self pruning which usually happens when there is an LAI higher than 7.
Leaf orientation affects light absorption. in low light conditions horizontal leaves captures more sunlight. In sunny conditions vertical leaves are less damaged by sun and allow light to reach lower leaves.

Question 62

The photosynthesis-water loss compromise

Answer 62

open stomates allow diffusion of CO2 into the leaf. But stomatal pores account for over 90% of the water lost due to evaporation. . Shoot adaptations represent compromises between enhancing photosynthesis and minimizing water loss.

Question 63

Resources from soil

Answer 63

water and minerals, plants must acquire water and minerals and transport them a short distance to vascular cylinder

Question 64

apoplast vs. symplast

Answer 64

the apoplast consists of everything external to the plasma membranes of living cells and includes cell walls, extracellular spaces, and the interior of dead cells such as vessel elements and tracheids. The symplast consists of the entire mass of cytosol of all living cells in a plant, as well as teh plasmodesmata

Question 65

Root architecture and acquistion of water and minerals

Answer 65

roots can respond to maximize nutrient uptake
“response” is growth and metabolism
High nutrient zone leads to root branching and increase production of proteins needed for assimilation and transport of nutrients.
Low nutrient zones roots grow through it with no/minimal branching
Root growth responds to neighbors. If roots detect themselves they don’t grow that direction. If they detect a different species they do high root growth for competition. if it is the same species detect (different plant) to is much less root growth.

Question 66

Plant nutrition often involves relationships with other organims

Answer 66

plants and soil microbes have a mutualistic relationship. Dead plants provide energy needed by soil-dwelling microorganisms. Secreations from living roots support a wide variety of microbes in the near-root environment (could be up to 30% GP “leaky roots”)

Question 67

Bacteria and plant nutrition

Answer 67

the layer of soild closely surrounding the plants roots in the rhizosphere. Rhizobacteria are free-living bacteria that occupy the rhizosphere.
Endophytes are nonpathogenic bacteria that live between the cells of host plant tissues
Endophytes and rhizobacteria depend on nutrients secreted by plant cells and in return help to enhance plant growth by: producing chemicals that stimulate plant growth, producing antibiotics that protect roots from disease, an absorbing toxic metals or increasing nutrient availability.
The species composition of bacterial communities living endophytically and in the rhizosphere vary widely by species… plants have a microbiome!

Question 68

Bacteria in the nitrogen cycle

Answer 68

nitrogen can be an important limiting nutrient for plant growth (most common limiting factor for terrestrials)
Plants can absorb nitrogen as either NO3-, or NH4+
Most soil nitrogen comes from actions of soil bacteria
the nitrogen cycle transforms nitrogen and nitrogen containing compounds

Question 69

closer nitrogen-fixing bacteria: a closer look

Answer 69

Nitrogen fixation is the conversion of nitrogen from N2 to NH3. It is energetically expensive and it makes usable nitrogen (ammonium). Reaction driven by nitrogenase enzyme.
Only bacteria do N-fixation. It only takes place with no oxygen present. Oxygen would mess up the equation.
Symbiotic relationships with nitrogen fixing rhizobium bacteria provide some plants species with a source of fixed nitrogen.
Along a legmes roots are swellings called nodules composed of plant cells “infected” by nitrogen-fixing rhizobium bacteria.
Plants can monitor benefits and shut off if not receiving enough benefits
The plant obtains fixed nitrogen from rhizobium and rhizobium obtains sugar and an anaerobic environment. Each legume species is associated with a particular strain of rhizobium
The development of nitrogen fixing root nodule depends on chemical dialogue between rhizobiu, bacteria and root cells of their specific plant hosts- cell signaling.