Download F - Mrs. GM Biology 200

Name ___KEY_________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014
Unit 8: Genetics & Heredity
Aside from these genetics problems, you can use "Problem Sets" from the Unit 8/9 webpage (answer keys are also on the
same page).
http://mrsg-mbiology200.wikispaces.com/Unit+08+%26+09--Genetics%2C+Heredity%2C+%26+Human+Genetic+Disorders+%28200%29

A pea plant is heterozygous (hybrid) for round seeds, a second pea plant has wrinkled seeds.
1. Which trait is dominant? ____round seeds______
2. Which trait is recessive? _____ wrinkled seeds _______________
3. Let R = ____ round seeds________________
4. Let r = _____ wrinkled seeds _______________
5. What is genotype of the pea plant with round seeds?
__Rr __
6. What is genotype of the pea plant with wrinkled seeds? __rr__
7. On the Punnett Square to the right, show the possible genotypes of
the offspring if these two pea plants were crossed.
8. What is the probability that these two plants will produce offspring
with wrinkled seeds? ____2____ out of 4

Human blood types are determined by three alleles. Because there are 3 alleles this is called multiple alleles.
9. The three alleles are: __ A__, __ B__, and __ o__.
a. The alleles for __ A__ and __ B__ are codominant and the allele for __ o__ is recessive.
10. Each person only inherits __ 2__ of the 3 alleles because we inherit __ 1__ allele from our mother and __1__ allele
from our father.
11. There are a total of six different genotypes:
a. If a person has type A blood, they can have the genotypes __ AA__ or __ Ao__.
b. If a person has type B blood, they can have the genotypes __ BB__ or __ Bo__.
c. If a person has type AB blood, they can only have the genotype __ AB__.
i. Why? b/c the alleles for A & B are codominant & are both expressed equally
d. If a person has type o blood, they can only have the genotype __ oo__.
Name ___KEY_________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014
i. Why? b/c the allele for o is recessive, and to be expressed, it must be homozygous (pure) since
even one dominant allele would “block” out the recessive allele

A biology student with Type o blood is surprised and shocked to learn that her father has Type A and her mother has
type B blood. (Use the symbols A, B, o to stand for each allele.)
12. What are the father's 2 possible genotypes if he has type A
blood?
o
__AA__ OR __Ao__
13. What are the mother's 2 possible genotypes if she has
type B blood?
o
__BB__ OR __Bo__
14. Is it possible that this student’s parents are both the true
biological parents? Use the Punnett Square to the right to
show if they could have a child with type o blood. (Use the
symbols A, B, o to stand for each allele.)
Yes, it is possible that both of the student’s parents are the true biological parents b/c if they are both heterozygous
for their blood types, they could have an offspring with a genotype of oo which would result in type o blood.
Unit 9: Human Genetic Disorders

In humans, colorblindness is a recessive seX-linked trait.
Let:




XC = allele for normal color vision
Xc = allele for colorblindness
Y = no allele
A man who is colorblind mates with a woman who is a carrier.
15. What is dad's genotype? __XcY__
16. What is mom's genotype? __XCXc___________
17. Use the Punnett Square to the right to show the possible
genotypes of their offspring.
18. What is the chance that any of their children will be colorblind? __ 2__ out of 4
Name ___KEY_________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014
Unit 10: Evolution
19. Define "evolution". theory that species (or populations) have changed gradually over time… evolves as allele
frequencies (%) (how often an allele occurs) change due to natural selection
20. Do individuals evolve? Explain you reasoning. No… an individual’s genes stay the same…
21. Do populations evolve? Explain your reasoning. Yes, b/c a population’s gene pool (total genes) may change
22. What are 4 types of indirect evidence for evolution? Fossil record, comparative anatomy, comparative
embryology, comparative biochemistry (DNA, amino acids, proteins)
23. What do we mean by "direct evidence" for evolution (examples of which are pesticide resistant insects and
antibiotic resistant bacteria)? Evidence of evolution that can actually be seen happening over a short period of time
24. Define & give examples of homologous structures. homologous structures are similar structures w/ modifications
(& are becoming more different… divergent evolution) & are evidence of common ancestor

ex. human arm, bat wing, bird wing, whale flipper… similar bone structures w/ some minor changes
25. Define & give examples of analogous structures. analogous structures are structures that have a similar function,
but not structure due to similar environment/use (becoming more similar… convergent evolution)… do NOT have
common ancestor ex. fly’s wing & bird’s wing… both for flying, but made differently (fly no bones & bird has bones)
26. Define & give examples of vestigial structures. vestigial structures are structures with reduced size or function &
often no apparent use anymore… evidence that organism has changed… ex. hip bones in whales, 3rd eyelid in human
27. What are Darwin's 4 main points related to his "Theory of Natural Selection". Give a brief description/example of
each. Overproduction (of offspring): more offspring are produced than survive, so that some may live to reproduce
Struggle to survive: more organisms than resources to go around leads to competition
Variation (w/in a population): range of traits w/in population due to… sexual reproduction, crossing over during
meiosis, arrangement of chromosomes during meiosis, mutations (NOT a response to the environment , just happen
to be useful)
Name ___KEY_________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014
Successful reproduction: those organisms w/ traits that are beneficial will be the ones that generally survive,
reproduce, & pass on their genes (“survival of the fittest”)… more offspring have favorable adaptation than before
Unit 11: Classification
28. Using the chart below, indicated the characteristics of organisms in each domain/kingdom.
3 Domain system
Archaea
5 kingdom system
prokaryotic (no nucleus)/
eukaryotic (nucleus)
unicellular (one cell)/
multicellular (more than one
cell)
autotrophic (makes own
food)/
heterotrophic (does not make
own food)
cell wall/
no cell wall
examples
Bacteria
Monera
Eukaryota (Eukarya)
Protista
Fungi
Plantae
Animalia
Prokaryotic
Eukaryotic
Eukaryotic
Eukaryotic
unicellular
Unicellular
(usually)
Multicellular
(usually)
multicellular multicellular
either
Either
heterotrophic autotrophic
Cell wall
NO cell wall
bacteria
Cell wall
(made of
chitin)
Amoeba,
Mushrooms,
Paramecium, molds, yeast
Euglena
Cell wall
(made of
cellulose)
Tree, grass,
flower
Eukaryotic
heterotrophic
NO cell wall
Human, dog,
Hydra, worm
29. What are the 8 taxa (groups) used for classification? Put them in order from broadest (most general) to narrowest
(most specific). Domain, kingdom, phylum, class, order, family, genus, species
30. If you are in the same family, are you definitely part of the same kingdom? _____(yes/no)_____
31. If you are in the same order, are you definitely part of the same genus? _____(yes/no)_____
32. What is "binomial nomenclature"? Linnaeus was the 1st to consistently use binomial nomenclature… 2 name
system… written as: Genus species or Genus species… Genus = 1st name, capitalized & species = 2nd name, lower
case & descriptive
• Ex. Common name
Genus & species
Name ___KEY_________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014
•
Humans
Homo sapiens
•
White Oak tree
Quercus alba
33. What is a "dichotomous key"? a tool used to classify organisms (or objects) by using paired opposing
statements/questions/characteristics
34. Use the key provided below to identify the creatures below. Write the “letter name” on the line to the left of the
object.
_B_
_A_
_E_
_D_
_C_
Creatures Dichotomous Key
1a. creature has a wide head……………………..go to 2
3a. creature has 3 eyes……………………………….B
1b. creature does not have a wide head…….go to 4
3b. creature does not have 3 eyes……………..C
2a. creature has a star on its body……………..go to 3
2b. creature does not have a star on its body…..A
4a. creature has a mouth……………………………D
4b. creature does not have a mouth…………..E
Unit 12: Ecosystems (& Populations)
35. Define and give an example of a "community" (in the scientific sense).
All of the organisms living & interacting in an area
ex. all of the people, cats, birds, worms, trees, etc. in Darien
36. Define and give an example of an "ecosystem".
All of the living & non-living things in an area
ex. all of the people, cats, birds, worms, trees, water, air, soil etc.
37. Define and give an example of a "population" (in the scientific sense).
Name ___KEY_________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014
All organisms of the same type living & interacting in an area
ex. all of the white oak trees in Darien
38. What is a limiting factor? limiting factors are circumstances or resources that limit growth, reproduction, or
distribution of organisms… provide environmental resistance & prevent population from growing indefinitely (stop
when reach “carrying capacity”)
39. Give examples of biotic limiting factors. Competition, predation, disease, symbiosis, etc.
Usually described
in terms of interactions especially who eats whom or trophic levels.
40. Give examples of abiotic limiting factors. Water, temperature, light, pH, salinity, oxygen, soil, nutrients, etc.
41. How do limiting factors affect population size? Limiting factors prevent population from growing indefinitely (stop
when reach “carrying capacity”)
42. Define "symbiosis". Symbiosis is when 2 species live closely together in a relationship over time.
43. Define and give an example of "commensalism". Symbiotic relationship in which one partner benefits from the
relationship & the other neither benefits, nor is harmed (+, 0)… ex. insect that eats fur that falls off of deer benefits
(+), deer is not affected (0)
44. Define and give an example of "mutualism". Symbiotic relationship in which both partners benefit from the
relationship (+, +). Ex. relationship between sea anemones & clownfish: the anemones provide the fish with
protection from predators & the fish defend the anemones against butterflyfish eat anemones
45. Define and give an example of "parasitism". Symbiotic relationship in which one partner benefits (parasite) & the
other is harmed (but not usually killed) (host) (+, -)… ex. mosquito (parasite) & human (host)
Name ___KEY_________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014
46. Define and give an example of "predation". Symbiotic relationship in which one partner benefits (predator) & the
other is harmed (killed) (prey) (+, -)… ex. hawk (predator) & mouse (prey)
Unit 13: Reproduction
47. How do offspring compare to their parent(s) genetically in asexual reproduction? ... in sexual reproduction?
In asexual reproduction they are genetically the same… In sexual reproduction they are genetically different…
48. Write the name of each numbered part on the line with the same number.
3
4
8
9
1
5
6
2
1. ____petal_________________________
3. ____stigma________________________
2. ____sepal_________________________
4. ____style__________________________
Name ___KEY_________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014
5. ____ovary_____________________________
8. ____anther_______________________________
6. ____ovule________________________________
9. ____filament_____________________________
7. = 3 + 4+ 5 together ____ pistil (carpel)_________
10. = 8 + 9 together ____stamen_________________
49. Write the name of the flower part that is described by each statement on the line.

The entire female structure of the flower _____pistil (carpel)______________________________________

The entire male structure of the flower ______stamen___________________________________________

The sticky tip (of the female structure) that helps trap pollen ____stigma____________________________

The part (of the male structure) that makes pollen _____anther______________________________

The long narrow tube (of the female structure) that pollen travels down to the egg ___style____________

The stalk (part of the male structure) that supports the part that makes pollen ___filament_______________

The swollen base (of the female structure) that contains the ovules ____ovary_______________________

The structure that (is neither female nor male and) protects the young flower bud ___sepal____________
Name ___ KEY _________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014

The part (of the female structure) where eggs are produced ____ovule_____________________________

The structure that (is neither female nor male and) is usually brightly colored and often scented (in order to
attract pollinators such as bees and butterflies) ____ petal________________________________
50. Label the parts of the male reproductive system diagram below by writing the letter from the diagram on the line
next to the name of the part. Letters will only be used once.
____B______ accessory glands
___D______ scrotum
____C ______ epididymis
___E_______ testes
____G______ penis
___F_______ urethra
___A_______ vas deferens
G
51. Write the name of the part of the male reproductive system that is described by each statement on the line.

tube that joins the epididymis to the urethra & transports mature sperm in preparation for ejaculation
_______vas deferens_____________________

add seminal fluids to sperm to form semen ___accessory glands_________________________

loose pouch of skin that hangs behind the penis; contains the testes & helps to regulate their temperature
______ scrotum______________________
Name ___ KEY _________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014

tube running through the penis that expels semen during ejaculation & carries urine from the bladder to
outside of the body (in males) ____urethra________________________

stores sperm & brings them to maturity (after formation) ___epididymis_________________________

produce sperm in seminiferous tubules _____ testes_______________________

used to insert sperm into the vagina _____penis_______________________
52. Label the parts of the female reproductive system diagram below by writing the letter from the diagram on the line
next to the name of the part. Letters will only be used once.
___E_______ cervix
___A_______ ovary
___B______ fallopian tube (oviduct)
___C_______ uterus
___D_______ vagina
E
53. Write the name of the part of the female reproductive system that is described by each statement on the line.

tube that joins the cervix to the outside of the body; also known as the birth canal
_________vagina___________________
Name ___ KEY _________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014

the lower part/opening of uterus; allows sperm to enter & menstrual blood to exit the uterus
________cervix____________________

narrow tubes attached to the upper part of the uterus; serve as tunnels for the eggs to travel from the ovaries
to the uterus, fertilization normally occurs here ______fallopian tube (oviduct)______________________

fertilized egg normally implants here; home to developing fetus (womb) ___uterus_______________________

small, oval-shaped glands; produce eggs & hormones _____ovary_______________________
Unit 14: Nutrition and Digestion
54. Label the parts of the human digestive system diagram below by writing the letter from the diagram on the line
next to the name of the part. Letters will only be used once.
____H______ anus
____K______ liver
____A______ salivary glands
____C______ epiglottis
____M______ mouth
____F______ small intestine
____L______ esophagus
____E______ pancreas
____D______ stomach
____J______ gall bladder
____B______ pharynx
____I______ large intestine
____G______ rectum
Name ___ KEY _________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014
A
M
B
A
C
L
K
J
D
E
I
F
G
H
55. Write the name of the part of the human digestive system that is described by each statement on the line.

produces bile ____liver________________________

helps moisten food, produces enzymes which are secreted into mouth ____salivary glands________________

produces enzymes which are secreted into the small intestine ___pancreas_________________________

flap that protects trachea (windpipe) when swallowing ___epiglottis_________________________
Name ___ KEY _________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014

food enters, mechanical digestion occurs, chemical digestion of carbohydrates/starches occurs
______mouth______________________

along with the pharynx (above it), connects mouth to stomach ______esophagus_____________________

Feces is stored here _____rectum_______________________

Used to eliminated feces from the body _____anus_______________________

mechanical digestion occurs, chemical digestion of proteins occurs, contains acid & enzymes
_____stomach_______________________

digestion of carbohydrates (starches), proteins, and fats is finished here, nutrients are absorbed into
bloodstream with the help of villi ____small intestine________________________

stores bile _____gall bladder_______________________

along with the esophagus (below it), connects mouth to stomach ____pharynx________________________

Water and salts are reabsorbed, solid feces is formed ____large intestine________________________
Unit 15: Transport
56. Label the parts of the human heart diagram below by writing the letter from the diagram on the line next to the
name of the part. Letters will only be used once.
____A______ aorta
____G______ left ventricle
____J______ right ventricle
____F______ AV valve
____B______ pulmonary artery
____H______ septum
____I______ inferior vena cava
____D______ pulmonary vein
____C______ SL valve
____E______ left atrium
____K______ right atrium
____L______ superior vena cava
Name ___ KEY _________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014
A
L
B
C
D
K
E
F
G
F
J
I
H
57. Write the name of the part of the heart/circulatory system that is described by each statement on the line.

oxygenated blood enters this heart chamber after coming from the lungs ____ left atrium ________________
Name ___ KEY _________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014

muscular wall that separates the left and right sides of the heart so that oxygenated and deoxygenated blood
don’t mix ____ septum_______________________________________________

vessel leaving the heart that sends deoxygenated blood to the lungs _____ pulmonary artery _____________

heart chamber that pumps oxygenated blood to the body ____ left ventricle ________________________

prevent blood from flowing backward ____ valves ________________________

vessels coming from the upper & lower body that bring deoxygenated blood back to the heart
________(superior & inferior) vena cava ______________________

oxygenated blood leaves the heart and goes to the body through this vessel ______ aorta ________________

deoxygenated blood enters this heart chamber after coming from the body ________right atrium ___________

vessel that bring oxygenated blood back to the heart from the lungs _______ pulmonary vein _____________

heart chamber that pumps deoxygenated blood to the lungs _____right ventricle_______________________
58. Name the three major types of blood vessels and describe their functions.
1. Arteries: move blood AWAY from heart (usually oxygenated blood except the pulmonary artery)
2. Capillaries: “connector” vessels, where exchange of materials occurs by diffusion
3. Veins: bring blood back to heart (usually deoxygenated blood except the pulmonary veins)
Name ___ KEY _________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014
59. Name the 4 components that make up blood and describe their functions.
1. Plasma: liquid portion that carries blood cells, nutrients, wastes, hormones, medicines
2. Red blood cells: carry oxygen (w/ help of hemoglobin)
3. White blood cells: immune response (fight of bacteria, germs)
4. Platelets: help heal wounds, involved in clotting
Unit 16: Gas Exchange and Excretion
60. Label the parts of the human respiratory system diagram below by writing the letter from the diagram on the line
next to the name of the part. Letters will only be used once.
___G_______ alveoli
___F_______ capillaries
____A________ nose
___I_______ bronchi
___C_______ larynx
____B________ pharynx
___H______ bronchioles
___E_______ lung
____C________ trachea
A
B
C
D
I
H
E
G
F
diaphragm
61. On the diagram above, draw in and label the diaphragm.
62. Write the name of the part of the respiratory system that is described by each statement on the line.

Also known as the voice box; lies between the pharynx and trachea ___larynx_________________________
Name ___ KEY _________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014

Large tubes that branch off of the main breathing tube and go into lungs carrying air ___bronchi____________

Passageway where air enters and exits body; air is moistened, warmed, & filtered here __nose______________

Connect nose to larynx and trachea ___ pharynx_________________________

Small sacs that fill with air during inhalation and are where gas exchange occurs; maximize surface area
_____alveoli_______________________

small tubes that branch off of the large branching tubes that bring air to the air sacs __bronchioles__________

main breathing tube (also known as the windpipe) that connects nose to large branching tubes; surrounded by
rings of cartilage; protected by epiglottis when swallowing ___trachea_________________________
63. Describe what happens to the diaphragm, ribcage, air pressure, & air (movement) during inhalation and exhalation.
What happens to the…
diaphragm
during inhalation
during exhalation
Moves down (contracts)
Moves up (relaxes)
ribcage
Moves up & out (expands)
Moves down & in (compresses)
air pressure
High outside & low in lungs
High in lungs & low outside
Into body
Out of body
Air (movement)
64. Label the parts of the human excretory (urinary) system diagram below by writing the letter from the diagram on
the line next to the name of the part. Letters will only be used once.
____C______ bladder (urinary bladder)
____A______ kidney
Name ___ KEY _________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014
____B______ ureter
____D______ urethra
A
B
C
D
65. Write the name of the part of the excretory system that is described by each statement on the line.

Store urine until released from body ______bladder______________________

Carries waste from kidneys to bladder _____ureter_______________________

Carries urine from bladder to outside of body _____urethra_______________________

Main organ that filters waste from the blood ______kidney______________________
66. Sketch a nephron (the best you can). Where are nephrons found? What is the nephron’s function?
Nephrons are found in the kidneys. (There are about 1 million nephrons per kidney.)
The nephron’s function (job) is to filter (cellular/metabolic) wastes from the blood.
Unit 17: Nervous Control
67. Label the parts of the nerve cell diagram below by writing the letter from the diagram on the line next to the name
of the part. Letters will only be used once.
Name ___ KEY _________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014
__B___ axon
__F___ Nodes of Ranvier
__C___ cell body
__E___ Schwann cell
__A___ dendrite
__G___ terminal buttons/end branch of axon
__D___ myelin sheath
F
D
E
B
C
D
A
E
F
B
G
68. Write the name of the part of the neuron that is described by each statement on the line.

fatty layer surrounding axon that protects it & allows impulses to move quickly ____myelin sheath__________

help send impulses to next neuron or effector (muscle, organ, gland) _terminal buttons/end branch of axon__

contain nucleus & cytoplasm ___cell body_______________________

receive impulses & move them toward cell body __dendrites______________________________________

sections of axon between Schwann cells not covered in myelin sheath; help transport impulses quickly
_____Nodes of Ranvier_____________________________

carries impulses away from cell body towards end branch ___axon_______________________________

make myelin ____Schwann Cell______________________________
69. What is another name for a nerve cell? neuron
Name ___ KEY _________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014
70. What is a synapse? Fluid filled space between the end branch/terminal buttons of one neuron and the dendrites
of the next neuron…. Impulses are sent across the synapse w/ the help of neurotransmitters.
71. What are neurotransmitters? What is the function of neurotransmitters? chemical messengers… they help
impulses cross the synapse & move from (the end branch/terminal buttons of) one neuron to the (dendrites of the)
next neuron
72. Describe the 5 steps in the reflex arc?
1.
2.
3.
4.
5.
Receptors detect stimulus & are activated
Sensory neuron transmits impulse towards spinal cord
Impulse crosses synapse to interneuron in spinal cord
From spinal cord impulse crosses synapse to motor neuron & leaves spinal cord
Impulse activates effectors (muscle, gland, organ) which responds appropriately
73. Is the brain involved in the reflex arc? NO!
74. Label the parts of the human brain diagram below by writing the letter from the diagram on the line next to the
name of the part. Letters will only be used once.
__B ___ cerebellum
__A___ cerebrum
__C___ medulla (stem)
__D___ spinal cord
75. Name the 3 main parts of the brain and describe their functions.
Cerebrum: speech, reasoning, emotions
Cerebellum: controls balance, posture, muscle tone
medulla (oblongata): part of the brain stem that controls involuntary actions of internal organs (heart rate, breathing
rate, peristalsis, etc.)
Unit 18: Movement
Name ___ KEY _________________
Mrs. Geithner-Marron
Date _________
Period ________
Biology 200 Final Exam REVIEW 2013-2014
76. What are the two main functions of the human skeletal system? Support & protection & help w/ movement
77. Which type of connective tissue holds bones to other bones? ligaments
78. Which type of connective tissue holds muscles to bones? tendons
79. What is the point where bones connect called? joint
80. Label the type of joint by writing the number from the diagram on the line next to the name of the part.
__ 5___ ball and socket
__3___ gliding
__4___ fixed
__1___ hinge
1
2
3
__2___ pivot
4
5
81. Give an example of each type of joint.
__shoulder, hip______ ball & socket
_wrist, ankle, hand, foot, vertebrae_ gliding
__skull_____________ fixed
__elbow, knee____________ hinge
__head w/ spine, lower arm__ pivot
82. Muscles always work in _____opposing____________________ pairs.
One muscle is a(n) ____flexor____________________________ and it bends the joint when it contracts.
The other muscle is a(n) _____extensor___________________________________ and it straightens the joint when it
contracts.