Accounting
Anthropology
Archaeology
Art History
Banking
Biology & Life Science
Business
Business Communication
Business Development
Business Ethics
Business Law
Chemistry
Communication
Computer Science
Counseling
Criminal Law
Curriculum & Instruction
Design
Earth Science
Economic
Education
Engineering
Finance
History & Theory
Humanities
Human Resource
International Business
Investments & Securities
Journalism
Law
Management
Marketing
Medicine
Medicine & Health Science
Nursing
Philosophy
Physic
Psychology
Real Estate
Science
Social Science
Sociology
Special Education
Speech
Visual Arts
Question
Particularly with regard to gas exchange, why do we have respiratory and cardiovascular systems, but flatworms, which are only a few cells thick, don't?
Answer
This answer is hidden. It contains 548 characters.
Related questions
Q:
As sperm are made, they travel through the vas deferens and are stored in the seminal vesicles until ejaculation.
Q:
Why is production of lung surfactant important for a baby?
A) Without lung surfactant, the baby's lungs do not develop properly.
B) Lung surfactant may block the placenta from exchanging oxygen.
C) Lung surfactant keeps the lung sacs from collapsing.
D) Lung surfactant keeps the lungs from sticking to the diaphragm.
Q:
Which of the following best describes the period during which the developing offspring is considered a fetus?
A) from fertilization to three weeks
B) from fertilization to eight weeks
C) the first trimester only
D) the third trimester only
E) from nine weeks until birth
Q:
An ectopic pregnancy is:
A) implantation of the embryo in the uterus.
B) another name for fraternal twins.
C) another name for identical twins.
D) attachment of an embryo outside the uterus.
Q:
Which of the following statements concerning sperm and fertilization is correct?
A) The first sperm that approaches the egg is the one to fertilize the egg.
B) Many sperm release their enzymes before one can get through.
C) The first capacitated sperm fertilizes the egg.
D) Several sperm must contribute their DNA to the egg for fertilization to occur.
Q:
A man has been experiencing reduced urine flow problems. After examination by his doctor, the diagnosis is an enlarged prostate gland. What is the connection between prostate enlargement and reduced urine flow?
A) The prostate is located where the ureters enter the bladder.
B) The prostate surrounds the urethra, the tube that transmits sperm and urine.
C) An enlarged prostate is a sign of cancer that affects the kidneys.
D) An enlarged prostate is a sign of cancer that affects the bladder.
Q:
Sperm development takes about:
A) 1 month.
B) 28 days.
C) 6 months.
D) 2.5 months.
Q:
The sequence of development of sperm is:
A) primary spermatocyte, secondary spermatocyte, tertiary spermatocyte, spermatid, sperm.
B) primary spermatocyte, spermatogonia, sperm.
C) immature sperm, mature sperm, secondary sperm, spermatocyte.
D) spermatogonia, spermatocyte, spermatid, sperm.
Q:
The vas deferens ducts empty sperm into the:
A) seminal vesicles.
B) epididymis.
C) uterus.
D) urethra.
Q:
Which structure would be best described as helping to prepare the female tract for pregnancy and maintain it during the early phases of pregnancy?
A) vagina
B) uterine tube
C) oocyte
D) corpus luteum
Q:
On average, about how often does ovulation occur?
A) every 6 months
B) every 28 days
C) every 14 days
D) every day
Q:
Through what structure does an oocyte travel on its way to the uterus?
A) uterine tube
B) cervix
C) vagina
D) ovary
Q:
If you could stop diffusion of substances in fruit fly zygotes, could you stop normal development? Why or why not?
Q:
Programmed cell death is also known as ________.
Q:
You are a substitute teacher in a high school biology lab class on the day the students are dissecting frogs. A particularly bright student happens to notice that the left adrenal gland is malformed in her frog. She asks if a problem in embryonic development could have caused that. Although there may be more than one reason, what might you propose as an explanation based on embryonic development?
Q:
Match the following. Answers may be used more than once.A) cleavageB) organogenesisC) gastrulationNeural tube forms
Q:
Match the following. Answers may be used more than once.A) cleavageB) organogenesisC) gastrulationArchenteron develops
Q:
Different cell layers may have different cell adhesion molecules.
Q:
Cells become more and more specialized as development progresses.
Q:
Eye cells can become beak cells once they are committed.
Q:
Bicoid is only one type of morphogen.
Q:
Cleavage and gastrulation take place in animals such as humans and birds but not in frogs.
Q:
The blastula is the stage of embryonic development in which cells migrate.
Q:
The end of a zygote that contains less yolk is the animal pole.
Q:
ZPA cells of the chick embryo produce which morphogen?
A) sonic hedgehog
B) sonic chicken
C) bicoid
D) chicken wing factor
Q:
Which of the following is a process by which an initial set of genes turns on a second set of regulatory genes, which eventually turns on a third set of genes?
A) developmental chain reaction
B) gastrulation
C) the sonic hedgehog sequence
D) the genetic cascade
E) somite production
Q:
What is the effect of higher concentration of bicoid protein in part of a fruit fly embryo?
A) It will develop into the posterior end of the organism.
B) It will develop into the heart of the organism.
C) It will develop into the head end of the organism.
D) It lowers the chances of embryo survival.
Q:
Of the choices listed, the first event that occurs during embryonic development is:
A) germ layer formation.
B) blastula formation.
C) organogenesis.
D) cleavage.
Q:
Which characteristic is typical of the vegetal pole of an embryo?
A) The vegetal pole is composed of a single, large cell.
B) The vegetal pole is always hollow.
C) The vegetal pole contains relatively less yolk.
D) The vegetal pole has a relatively greater proportion of yolk.
E) The vegetal pole is the site of the development of the mouth.
Q:
The phase during which embryonic cells arrange themselves into three layers is called:
A) cleavage.
B) gastrulation.
C) organogenesis.
D) fertilization.
E) induction.