exam 2 Flashcards
1
Q
what are the characteristics of animals?
A
eukaryotic
multicellular
heterotrophic (ingest)
motile at some stage
lack structural cell walls
embryo passes through blastula stage
2
Q
animal diversity
A
- animals are multicellular heterotrophs with no cell walls; diverse in form
- inhabit every conceivable habitat
- locomotion is a distinctive characteristic (some are sessile)
- up to approximately 40 phyla
3
Q
what are cells held together by
A
collagen (a protein of connective tissue)
4
Q
cells are often _________
A
flexible, they have intercellular junctions
5
Q
how many animals are invertebrates
A
99%
6
Q
where can animals live
A
marine, freshwater, terrestrial, or aerial. they can also live in hosts
7
Q
all animals…
A
- are gametes formed by meiosis
- fuse almost immediately to form diploid zygote
- gametes do not go through mitosis
- do not alternate generations
8
Q
what forms of locomotion can animals have
A
swimming, walking, flying, gliding, slithering, rolling
9
Q
what three features define an animal’s body plan?
A
- the number of tissue types in embryos
- they type of body symmetry (radial vs. bilateral)
- the way in which the earliest events of embryo development proceed
10
Q
how can animals be categorized by the amount of tissues they have?
A
- no specialized tissues
- diploblasts (endoderm & ectoderm)
- triploblasts (ectoderm, endoderm, and mesoderm)
11
Q
what cells in sponges allow them to recreate their sponge shape no matter what happens to it?
A
totipotent cells
12
Q
ectoderm
A
the “covering” of the animal
- skin
- nervous tissue
13
Q
endoderm
A
inner most layer of skin; eg. digestive tract
14
Q
mesoderm
A
tissues in the organism
- muscle
- bone
- circulatory system
15
Q
why do these tissue differences matter?
A
- increased cellular complexity
- increased tissue diversity
- allowed for coelomic evolution
16
Q
what are the three types of symmetry?
A
- asymmetric
- radial symmetry
- bilateral symmetry
17
Q
radial symmetry
A
multiple planes of symmetry
18
Q
bilateral symmetry
A
one single plane of symmetry and they face their environment in one way
19
Q
protostomes
A
two holes in early development, mouth forms first
20
Q
deuterostomes
A
two holes form in early development, anus forms first
21
Q
who are deuterostomes
A
phyla chordata and echinodermata
22
Q
ecdysozoa
A
animals that molt
23
Q
lophotrochozoa
A
most either have lophophore (a fan of ciliated tentacles around the mouth) or trochophore (two bands of cilia around their middle) larvae
24
Q
animal phyla
A
porifera (sponges)
cnidaria (jellyfish)
platyhelmenthes (flat worms)
molluska (clams)
annelida (segmented worms)
nematoda (round worms molt)
arthropoda (bugs)
chordata (vertebrates)
echinodermata (sea urchins)
25
what phyla are fungi in?
opisthokonta
26
how do fungi eat
they digest their food (by secreting enzymes into their food) and then they ingest it
27
what are fungi cell walls made of
chitin
28
what is the only spore dispersing organ
the mushroom. the majority of of the fungal body is unseen
29
which of the following is a trait shared by animals and fungi?
A. both make cell walls from cellulose
B. Both have a swimming appendages that do breaststroke
C. Both taste like chicken
D. Both are heterotrophs
E. Both are multicellular
D
30
what are the fungi phyla
Chytridiomycota (swimming spores)
Zygomycota (zygospores)
Glomeromycota (friends of plants)
Basidiomycota (basidiospores)
Ascomycota (ascospores)
31
zygomycetes can make spores through.......
mitosis.
32
chytridiomycota
overall "harmless" decomposers, swimming spores, and caused a huge strain of deaths in amphibians in their skin.
32
what are the common places of zygomycetes
on food and often cause food spoilage
33
zygomycota
have zygospores (a tough and resilient that can survive the dry environment of land)
33
glomeromycota
form endomycorrhizial mutualisms with roots of land plants. without their help, many land plants would not survive on land.
34
basidiomycota
mushrooms with the gills underneath the cap. makes basidiospores that are made from a spore producing structure called the basidium
35
ascomycota
have mushrooms with a wrinkly cap, more surface area. have a spore producing sac called the ascus which contains them as well.
36
what forms can fungi switch between?
yeast and filamentous forms
37
how can fungi help protect/help humans?
they can make antibiotics like penicillin
38
many basidiomycota and ascomycota are also what?
parasites or pathogens on plants and animals (ringworm, athletes foot, etc)
39
how do basidiomycota and ascomycota interact positively with plants?
lichens are associations between a fungal "mycobiont" and "phycobiont"
40
mycobiont
ascomycete
41
phycobiont
cyanobacteria
42
what do basidiomycetes and ascomycetes also participate in?
ectomycorrhizal associations with the roots of plants
43
binary fission
splitting a cell in half
44
what are some advantages to asexual reproduction?
- it is fast; simple nuclear division followed by cytokinesis
- all cells/individuals can reproduce; no mate finding
- favorable gene combinations are maintained.
45
what are some disadvantages to asexual reproduction?
- in a changing environment, adaptation is severely restricted by asexual reproduction.
- risk of extinction by biotic interactions
- no way to mask harmful genes
46
what are some advantages to sexual reproduction?
- genetic diversity and variance
- better at dealing with and responding to antagonistic biotic interactions (predation, competition, etc.)
- reduces the expression of potentially harmful genes.
47
what are some disadvantages to sexual reproduction?
- its slow: it is costly to the rate of reproduction
- male and female gametes must be brought into contact
- recombination breaks up favorable gene combinations
48
asexual reproduction
processes in which new individuals are derived from only one parent and without the fusion of gametes. there are two types: parthenogenesis and fission
49
parthenogenesis
females produce unfertilized eggs through mitosis that develop through mitosis. (offspring are genetically identical to the adult) (diploid)
50
fission
reproduction by detachment and subsequent differentiation of groups and mitotically derived cells or tissues (bud off and split)
51
obligate parthenogenesis
when organisms like rotifers and darwinulid ostracods only experience asexual reproduction
52
what makes organisms alternate between sexual and asexual reproduction?
environmental cues like water quality, food availability and day length
53
sexual reproduction
reproductive process in which the recombination of genetic material derived from more than one parent is possible
54
meiotic parthenogenesis
development of a new individual (male or female) from an unfertilized 'egg'.
55
sexual reproduction with fertilization
process of reproduction in which meiotically derived haploid eggs and spermatozoa fuse to create a diploid zygote
56
gonochorism (dioecy)
sexes are separated and individuals are either exclusively male or female.
57
hermapphroditism (monoecy)
the same individual can function as both male and as female
58
simltaneous hermaphrodite
both male and female gametes are produced in the individual at the same time
59
sequential hermaphrodites
a sexual reversal takes place over time (male and female gametes produced at different times)
60
protogyny
female to male
61
indirect development
several larval stages
61
protandry
male to female
62
direct development
no larva; juvenile is hatched or born resembling the adult
63
external fertilization
no mate choice, less effort, less risk
64
internal fertilizaton
allows mate choice, energetically costly, risky
65
what is the evolutionary sequence leading to sexual reproduction in animals and land plants?
1. asexual reproduction
2. acquisition of mechanisms for limited recombination of genetic material
3. meiosis
4. the evolution of separate mating types
5. anisogamy (the adoption of small mobile and larger gametes)
6. separation of the male and female functions in different individuals
66
land plants
a monophyletic group whose common ancestor was an archaeplastid organism that made it on to land
67
plastid
an organelle that is the result of another endosymbiosis with a cyanobacteria
68
rhodophyta (red algae)
- multicellular
- sexual reproduction
- chlorophyl d
69
glaucophyta (walled plastids)
- unicellular
- only asexual reproduction
70
viridiplantae (plants and pals)
- chlorophyl B
- sexual reproduction
- lack of peptidoglycan
71
which eukaryotic clades have photosynthetic members?
stramenopila, alveolata, rhizaria, archaeplastida, discoba
72
how are secondary plastids made
- host cell engulfed a red alga that was capable of photosynthesis.
- the red alga found a home when the food vacuole fused with the hot ER and was safe from digestion.
- symbiotic relationships were established and the red alga becomes the secondary plastid as the host takes over more and more functions.
- they are surrounded by more membranes
73
how do plants allow for nutrient absorption without drying out?
the waxy, waterproof cuticle prevents evaporation from upper surface, but they still move up through the bottom side.
74
how do plants deal with solar UV-radiation?
water absorbs and scatters most of the UV light to help prevent damage of DNA and other cellular components.
75
how to maintain gas exchange with that wax with that wax on the upper surface
specialized epidermal cells called guard cells form an opening (stomata) which lets plants open and close.
76
what are the adaptations in plants
cuticles, stomata, vascular tissues, complex leaves, seeds, flowers and fruits
77
what do vascular tissues do?
move water and nutrients up from the soil into the rest of the plant (xylem) and sugars bidirectionally (phloem)
78
mitosis
diploid to diploid (two identical copies of parent cells)
79
meiosis
diploid to haploid (four unique daughter cells)
80
fertlilzation
gametes fusing together with other compatible gametes
81
how do spores reproduce?
they reproduce directly and do not undergo fertilization
82
isogamy
gametes that look the same
83
anisogamy
gametes that look different
84
zygote
what the gametes are after fusion. they can either perform meiosis and produce spores (become multicellular) or start mitosis to make progeny
85
how do zygotes become embryos?
by being retained by "mom" and going through a series of mitotic divisions
86
gametic (diploid dominant) life cycle
"meiosis, then fertilization"
in most animals, some SAR, some fungi, some amoeba
- diploid phase
- meiosis to make haploid phase (gametes)
- fertilization to make diploid zygote
- plasmogamy
- karyogamy
-mitosis to make progeny diploid phase
87
zygotic (haploid dominant) life cycle
"fertilization, then meiosis"
in most amoeba, most multicellular SAR, some fungi, most green algae
- haploid phase
- mitosis to make haploid gametes
- fertilizationto make diploid zygote
- plasmogamy
- karyogamy
- meiosis to make progeny haploid phase from meiospores
88
c-fern and other land plants life style
alternation of generations
- haploid phase
- mitosis to make haploid gametes
- fertilization to make diploid zygote
- mitosis to make diploid phase
- diploid phase
- meiosis to make haploid spores
- mitosis to make progeny hploid multicellular phase
89
are mosses gametophyte or sporophyte dominant?
gametophyte dominant
90
are ferns gametophyte or sporophyte dominant?
sporophyte dominant
91
where are spores produced?
anthers
92
dikaryotic life cycle
" delay of karyogamy"
- haploid phase
- start of fertilization makes dikaryon
- plasmogamy
- mitosis makes dikaryotic phase
- dikaryotic phase
- end of fertilization makes diploid
- karyogamy
- meiosis to make haploid spores
- mitosis to make progeny haploid phase
93
how is the support systems in vertebrates formed?
by cells that produce connective tissues that provide structure and binding sites for muscle
94
types of animal skeletons
spicules
hydrostatic skeleton
exoskeleton
endoskeleton
95
spicules
structure of sponges
96
hydrostatic skeleton
- mostly found in aquatic or soil dwelling organisms
- support derived from the pressure of the fluid within the organism
- usually between phylum nemotoda, platyhelmenthese, and annelida
97
exoskeletons
- provide external covering for support and protection. - found in most arthropods and most mollusks
- mostly made of calcium carbonate
98
what adaptations for defense has the exoskeleton evolved from
- thick to avoid being crushed
- spines to dissuade predators
- crypsis (camouflage)
- constitutive defenses (defenses that are always present)
- inducible defenses (defense brought about by the presence of a predator)
99
endoskeleton
- provides internal support and protection
- composed of CaCO3 and connective tissue in the echinodermata
- composed of calcium phosphate or cartilage in chordata
100
chondrocytes
secretion and maintenance of matrix
101
matrix
firm gel-like substance
102
advantages to growth in plants
- greater reach for resource acquisition
- harder for consumers to kill you
- decreased surface area per unit volume
- good for holding temperature
- good for decreasing water loss
103
disadvantages to growth in plants
- requires use of additional resources
- bigger reward for consumers
- decreased surface area per unit volume
- less exchange with the surrounding environment
104
3 major organs in plants
1. leaves
2. stems
3. roots
leaves and stems make up the shoot system
105
stems
made of nodes and internodes branches are produced at the nodes
106
roots
simple branched structures; no nones or internodes.
107
challenges of multicellularity
- sticking together
- communication
- coordinated activities
108
communication in plants
- plant cells are surrounded by a rigid wall woven from cellulose strands
- plasma membrane and the cell's contents are pushed up against cell wall
- adjacent cell walls are cemented together by middle lamella
- tunnels through walls allow for connection of plasma
109
properties of water
- selectively permeable membrane allows movement of water but not solutes
- water always moves to equalize solute concentration
- "tries to" dilute the more concentrated solution
110
turgor pressure
plump cells in plants that provides the most support in non-woody plant parts
111
parenchyma
the name for plant tissues made of cells with just a primary cell wall
112
collenchyma
cells have unevenly thickened primary walls
113
sclerenchyma
cells have a thick secondary cell wall
114
three tissue system:
dermal: protection, mostly on the outside
vascular: transport of materials (xylem and phloem)
- veins in leaves and other structures
ground: everything else; most living cells, basic physiology
115
primary growth
the production of non-woody stems, roots, and leaves. occurs from root shoot apical meristems (growth point)
116
bud primordia and axillary buds
- bud primordia develop into axillary buds
- each axillary bud contains a dormant meristem that is prevented from growing by chemicals secreted by SAM.
- an axillary bud may start growing a lateral shoot (new branch)
117
root apical meristem
- at the tip of a growing root, protected by a root cap
- some of the cells produced in the root apical meristem replace root cap cells being sloughed off
- the rest form the growing root
118
what does the primary growth form?
epidermis, ground tissues, and vascular bundles
119
what makes plant growth intermediate?
- adding on modules, year after year
- other factors like wind, slope, and light availability
120
what is secondary growth?
increase in girth of the plant. requires two lateral, secondary meristems (vascular cambium and cork cambium)
121
woody growth
durable tissues with chemical composition that makes them rigid and resistant to decay
122
annual plants
entire life cycle is in a single season
123
biennial plants
two seasons to complete the life cycle; large root and short stem survive into second year
124
herbaceous perennials
regrow each year from a bulb or not
125
what plants do true secondary growth?
ginko, cyads, gnetales, pinaceae, and cupressophytes in Gymnosperms
shrubs, trees, and woody vines in anthophyta
126
vascular cambium
- results in the formation of wood and inner bark
- produces secondary xylem and phloem
127
what is the difference between xylem and phloem
xylem is produced towards the center and phloem is produced towards the edge. accumulation of xylem pushes phloem outward, resulting in increase of thickness in stem
128
Xylem
function: main conducting tissue for water and minerals absorbed by roots
composed of: parenchyma cells, fibers, vessels, tracheids, and ray cells.
129
tracheids
tapered cells that are no open on the ends. dead at maturity and often have pits between them
130
vessels
long tubes composed of end-to-end vessel elements, which are open at each end, often with strips of wall material across opening. dead at maturity
131
rays
function in food storage and lateral conduction
132
difference between gymnosperm xylem and anthophyte xylem
g. xylem has tracheids only and a. xylem has both tracheids and vessel elements and fibers
133
phloem
function: conducting photosynthates (dissolved foods, mostly sugars, produced by photosynthesis)
composed of: sieve tube members and companion cells, but also has fibers, parenchyma, and ray cells
134
sieve tube members
- living cells, but lack nuclei at maturity
- cylindrical cells, laid end-to-end (like vessel elements to form sieve tubes
- ends have sieve plates that are full of small pores through which cytoplasm extends between cells
135
periderm
- results in the formation of outer bark
- 3 parts of periderm:
1. cork cambium
- meristematic; multiple origination events
2. cork
- protective tissue to the outside of cork cambium,
dead at function of maturity
3. phelloderm
- phellos = cork
- living cells to the inside of cork cambium
136
bark
outer bark = periderm; mostly dead cells (isolated by suberinized cork cells
inner bark = phloem; all living cells
137
heartwood
- darker
- non-conducting
- filled with secondary metabolites like resins and tannin
- no food reserve, all dead cells
138
sapwood
- lighter
- conducting
139
early wood
- spring
- larger cells
- thinner walls
- fast growing
- lighter
140
late wood
- fall
- smaller cells
- thicker walls
- slow growing
- darker
141
advantages for increased size among animals
- larger size can confer greater immunity from consumption by other animals
- larger animals tend to be able to displace smaller animals from limited shared resources
142
digestion
the mechanical and chemical breakdown of organic food into small unit for absorption by the consumer.
143
assimilation of food
the absorption of digested nutrients to form complex organic protoplasmic materials
144
animal energetics
- the width of the energy path is proportional to the amount of energy at that point
- as food energy goes through the digestive and assimilative process there is a progressive loss of energy
- growth and reproduction are allocated energy after respiration costs are met
145
advances in digestion
- it is intracellular in heterotrophic "protists" and sponges
- food particles are taken into vacuoles through phagocytosis
- digestive enzymes delivered by lysosomes
- waste is released by exocytosis
146
limitations of intracellular digestion
- only small particles can be phagocytized
- each cell must be capable of secreting all necessary enzymes
- each cell needs to be able to incorporate the metabolites into their protoplasm
147
3 regions of a generalized invertebrate gut
1. anterior foregut (ectodermal origin)
2. absorptive midgut (endodermal)
3. posterior hindgut (ectodermal)
148
benefits to a digestive system with 2 openings?
- can consume >1 prey at a time
- more areas for processing
- can absorb more diversity of food, proteins, carbs, and fats
149
gut modifications in herbivores
- elongated hindgut to increase surface area of absorption
- valves present to slow passage and increase surface area
- extremely complex in mammals
- rumen present in most
- enlarged colon
150
ruminants
- cattle, sheep, and goats
- bacteria in a special compartment in the rumen
151
non-ruminants
- horse, rabbits, and rats
- enlarged large intestine and caecum, called a functional caecum
152
rumen
an anaerobic, fermentation vat
153
reticulum
receives smaller material for further breakdown
154
omasum
absorbance of fatty acids and bicarbonate
155
abomasum
"true glandular stomach" -- acidic but specialized for processing bacteria
156
caecum
site of bacterial fermentation
157
coprophagy
rabbits and many rodents eat their fecal pellets and give their food a second pas to extract additional nutrients
158
what are the similarities between fungi and plants?
both groups rely extensively on turgor pressure (osmotic pumps) and cell walls to support their bodies
159
what are some differences between food storage in fungi and plants?
- most fungi store their food as glycogen
- plants store their food as starch
160
characteristics of fungal metabolism
- fungi are heterotrophic
- fungi digest then ingest
- fungi produce exoenzymes to accomplish
161
how do fungi digest their food
secreting enzymes into the substrate, releasing sugars, amino acids, etc. active transport of the food near the tip of the mycelia creates a high concentration of solutes
162
what can the hyphal tip do for the mushrooms
1. new membrane for tip growth
2. chitin for cell walls
3. exoenzymes for digestion
163
septae
partial cross-walls formed in basidiomycota and ascomycota (dikaryotic fungi)
164
ectomycorrhizae
relationships between plants and fungi
- some asco and basio form these relationships with woody plants
165
advantages of having spores in fungi
- produced in enormous numbers
- spread over a wide area (by wind)
- can remain dormant until conditions become favorable (sometimes years)
- both sexual and asexual spores may be produced, depending on the species and condition
166
what processes happen in the cytosol?
glycolysis, pyruvate oxidation, and fermentation
167
what processes happen in the mitochondrion?
electron transport chain
168
how does o2 get to the electron transport chain?
gets to cells from diffusion (passive transport)
169
cytoskeleton
- a system of tubules and filaments that support & maintain the structure of the cell
- made from the protein actin
- actin interacts with other proteins like myosin to move macromolecules in the cell
170
3 principle ways a substance can enter across the plasma membrane
1. diffusion along the concentration gradient
2. mediated transport systems through specific binding sites on a trans-membrane protein
3. endo- and exocytosis where materials are moved with a membrane bound vesicle
171
what does aerobic metabolism depend on
O2 being made available to respiring tissues
172
transport in porifera
- digestion is completely intracellular
- diffusion is successful, no excretory or respiratory organs
173
transport in cnidarians
- mouth opens to gastrovascular cavity
- lack excretory and respiratory systems
- rely on diffusion and "muscular" contraction for material movement
- digestion starts extracellularly in the gastrovascular cavity, but nutritionally is intracellular digestion at the gastrodermis
174
transport in platyhelmenthes, nematodes, and annalida
- rely on diffusion
- fluid-filled cavity (coelom) for nutrient distribution
- transport via muscle contractions
- fluid had oxygen binding molecules like hemoglobin
175
what does counter current exchange aim to do?
maximize the efficiency of transfer of O2
176
fick's law
QO2 = ∆PO2 * k * A/L
177
what does each part of fick's law mean
∆PO2 = the difference between the internal concentration of O2 and the concentration of O2 immediately adjacent, but outside the exchange surface
A = the total exchange surface across which O2 can diffuse
L = the distance molecules must diffuse (thickness of gills, etc)
k = a diffusion coefficient characteristic of the material diffusing across the exchange surface.
178
function of circulatory system
carry a transport fluid into close contact with every cell in the body
179
evolution of transport systems
- increased capacity for O2 uptake
- allows the 1mm limitation to be lifted
- removes O2 from respiratory surfaces and maintains a steep ∆PO2 (oxygen gradient)
180
2 circulatory systems
open and closed
- both require muscular pumps and/or muscular, pulsating blood
vessels
181
open circulatory systems
- hemolymph as transport fluid
- composed of water, salts, organic carbs, proteins, and lipids
- few have hemoglobin to store O2
- heart as pump with some blood vessels
- overall pressure is low in the system; good for sedentary organisms with low O2 demands
182
tube heart
it is made up of a number of linearly arranged chambers. allows for a large amount of blood to flow into and out of the surrounding sinus.
183
benefits of an enclosed system
- allows for enough pressure to maintain a high flow rate
- precise alteration of blood flow
- two circuits (pulmonary and systemic) run on one pump
184
complexity of heart systems
fish, frogs, turtles, lizards, crocodiles, birds, mammals
185
pulmonary circuit
1. blood returns to the heart from the body entering the right atrium
2. blood enters the right ventricle
3. blood is pumped from right ventricle to lungs
186
systemic circulation
1. blood returns to the left atrium from lungs
2. blood enters the left ventricle
3. blood is pumped from the left ventricle to the body
187
cardiac muscle
- striated
- arranged in parallel
- connected in series
- gap junctions
188
arteries
carry blood away from the heart to the capillaries
- blood leaves the heart under high pressure
- much thicker and more elastic to accommodate this
pressure
189
veins
carry blood to the heart after it passes through the capillaries
- after exiting the tissues, blood is under relatively low pressure
- much thinner walls and much larger interior diameters
190
2 factors that aid in this transport
- skeletal muscle contractions
- presence of valves in the veins
191
swim bladder in fish
a gas-filled space which is the most efficient flotation device that is absent in tunas, some abyssal fishes, and most bottom dwellers. a fish can control depth by controlling how much gas is in the bladder
192
fish gills and how they are countercurrent
water flow is perpendicular to blood flow; this exchange maximizes exchange of gasses
193
countercurrent heat exchange
the arteries of our arms and legs run parallel to a set of deep veins. as warm blood passes down arteries, the blood gives up some of its heat to the colder blood returning from extremities in these veins
194
what is optimized for photosynthesis, fluid transport, and gas exchange?
leaves!
195
palisade mesophyll
cells near the top of leaves that are thin, tall, and tightly packed
196
spongy mesophyll
cells are more unevenly shaped and surrounded by air spaces
197
what makes a stomata open
active transports of solutes into cells results in water moving in, which in turn increases turgor pressure
198
which way does water move through xylem
along its concentration gradient
199
what moves through the phloem?
sap (sugar) and water. They move down the concentration
200
two ways that water moves between plant cells
- apoplast: outside cell membranes
- symplast: inside cell membranes (required to cross endodermis)
201
waterproofing Casparian Strip
in the roots that forces water to have to move through cells, rather than around the cells in the wall
202
in the root cortex, the water can either:
1. move around the cells through the large pores in the wall (apoplastic movement)
2. move through the cells by using cytoplasmic connections called plasmodesmata (symplastic movement)
203
osmosis
water moves from an area of high water potential (low solute concentration) to area of low water potential (high solute concentration)
204
cohesion
water molecules tend to stick to one another
205
adhesion
water molecules tend to stick to other polar molecules
206
capillarity
a consequence of adhesion, cohesion, and properties of tubes. decreases the amount of pull needed to move water upwards.
207
how does water get to the tops of trees
evaporation of water from leaves leads to increased solute concentration in the mesophyll cells of the leaves. the concentration of ions in the leaves in increased, water from xylem moves into mesophyll cells. this reduces pressure in the xylem, which draws water up.
208
what is the only thing that sugar can flow through
the phloem dissolved in water. water has to constantly move from the xylem to the phloem to keep the phloem sap flowing.
209
source
usually leaves but could be storage root
210
sink
any growing, storing, or metabolizing tissue
211
assimilates
products moving from source to sink
212
what is the direction of movement of substances
bidirectional
213
what does pumping water to the shoot do
provides the water necessary to drive the flow of sugar down the phloem
