Essential Idea
Challenge:
Hormones are used when signals need to be widely distributed.
6.6 Hormones, homeostasis and reproduction
Understandings
Syllabus Reference
| Statement | Guidance |
6.6.U1 | Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration. | |
6.6.U2 | Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature. | |
6.6.U3 | Leptin is secreted by cells in adipose tissue and acts on the hypothalamus of the brain to inhibit appetite. | |
6.6.U4 | Melatonin is secreted by the pineal gland to control circadian rhythms. | |
6.6.U5 | A gene on the Y chromosome causes embryonic gonads to develop as testes and secrete testosterone. | |
6.6.U6 | Testosterone causes pre-natal development of male genitalia and both sperm production and development of male secondary sexual characteristics during puberty. | |
6.6.U7 | Estrogen and progesterone cause pre-natal development of female reproductive organs and female secondary sexual characteristics during puberty. | |
6.6.U8 | The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones. | The roles of FSH, LH, estrogen and progesterone in the menstrual cycle are expected. |
| Statement | Guidance |
6.6.U1 | Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration. | |
6.6.U2 | Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature. | |
6.6.U3 | Leptin is secreted by cells in adipose tissue and acts on the hypothalamus of the brain to inhibit appetite. | |
6.6.U4 | Melatonin is secreted by the pineal gland to control circadian rhythms. | |
6.6.U5 | A gene on the Y chromosome causes embryonic gonads to develop as testes and secrete testosterone. | |
6.6.U6 | Testosterone causes pre-natal development of male genitalia and both sperm production and development of male secondary sexual characteristics during puberty. | |
6.6.U7 | Estrogen and progesterone cause pre-natal development of female reproductive organs and female secondary sexual characteristics during puberty. | |
6.6.U8 | The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones. | The roles of FSH, LH, estrogen and progesterone in the menstrual cycle are expected. |
6.6 Hormones, homeostasis and reproduction
Understandings
Syllabus Reference
6.6 Hormones, homeostasis and reproduction
Application and Skills
Syllabus Reference
| Statement |
6.6.A1 | Causes and treatment of Type I and Type II diabetes. |
6.6.A2 | Testing of leptin on patients with clinical obesity and reasons for the failure to control the disease. |
6.6.A3 | Causes of jet lag and use of melatonin to alleviate it. |
6.6.A4 | The use in IVF of drugs to suspend the normal secretion of hormones, followed by the use of artificial doses of hormones to induce superovulation and establish a pregnancy. |
6.6.A5 | William Harvey’s investigation of sexual reproduction in deer. William Harvey failed to solve the mystery of sexual reproduction because effective microscopes were not available when he was working, so fusion of gametes and subsequent embryo development remained undiscovered |
6.6.S1 | Annotate diagrams of the male and female reproductive system to show names of structures and their functions. |
6.6 Hormones, homeostasis and reproduction
Vocabulary
6.6 Hormones, homeostasis and reproduction
Guiding Questions
Do Now
6.6 Hormones, homeostasis and reproduction
What is the endocrine system?
Hormones are secreted directly into the blood by glands.
They are carried to the target organ or tissues (the place of intended action).
The action of the hormone changes the condition of the tissue.
This change in monitored through feedback.
Most hormonal change results in negative feedback.
Key endocrine glands:
6.6 Hormones, homeostasis and reproduction
What are the key endocrine glands?
6.6 Hormones, homeostasis and reproduction
What is homeostasis?
Homeostasis literally means “same state” - refers to the process of keeping the internal body environment in a steady state.
Very important - a great deal of the endocrine system and autonomic nervous system is dedicated to homeostasis.
Homeostasis is the state of steady internal, physical, and chemical conditions maintained by living systems
6.6 Hormones, homeostasis and reproduction
What needs to be controlled?
6.6.U1 Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration.
All of these factors are maintained between limits within the blood and tissue fluid.
7.35 to 7.45
37.0oC
70 - 100 mg/dL
6.6 Hormones, homeostasis and reproduction
6.6.U1 Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration.
Controlled by the pancreas.
Glucose receptor cells monitor the concentration of glucose in the blood.
Endocrine cells (called the islets of Langerhans), which secrete hormones.
α cells secrete glucagon
β cells secrete insulin.
The two hormones are antagonistic, and have opposite effects on blood glucose.
6.6 Hormones, homeostasis and reproduction
6.6.U1 Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration.
We ‘beta’ store the excess glucose
6.6 Hormones, homeostasis and reproduction
6.6.U1 Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration.
‘Gluc-a-gone’
6.6 Hormones, homeostasis and reproduction
glycogen
glucose
Increase in blood sugar
High blood sugar
promotes insulin release
promotes glucagon release
Low blood sugar
Glucagon
Insulin
stimulates breakdown of glycogen
stimulates formation of glycogen
Decrease in blood sugar
Stimulates uptake of glucose by cells
α cells
β cells
Concentration is therefore strictly controlled within a range of 80-100 mg 100cm-3
Very low levels (hypoglycaemia) or very high levels (hyperglycaemia) are both serious and can lead to death.
6.6 Hormones, homeostasis and reproduction
6.6 Hormones, homeostasis and reproduction
Explain the control of blood glucose (8 Marks)
6.6.U1 Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration.
6.6 Hormones, homeostasis and reproduction
6.6.U1 Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration.
6.6 Hormones, homeostasis and reproduction
Diabetes is a disease caused by a failure of glucose homeostasis.
6.6.A1 Causes and treatment of Type I and Type II diabetes.
Insulin-dependent diabetes (type 1 or early onset diabetes) - a severe insulin deficiency due to autoimmune killing of β cells (possibly due to a virus).
Non insulin-dependent diabetes (type 2 or late-onset diabetes) - insulin is produced, but the insulin receptors in the target cells don’t work, so insulin has no effect.
6.6 Hormones, homeostasis and reproduction
6.6.A1 Causes and treatment of Type I and Type II diabetes.
In both cases:
- high blood glucose concentration after a meal,
- Glucose is not reabsorbed by kidneys
- much of the glucose is excreted in urine
- osmosis causes water to follow producing large quantities of dilute urine
- less glucose for cells means that proteins are metabolised in respiration
- organ damage follows
Diabetes mellitus means “sweet fountain” - doctors used to test for diabetes by tasting urine!
6.6 Hormones, homeostasis and reproduction
6.6.A1 Causes and treatment of Type I and Type II diabetes.
Diabetes can be treated by injections with insulin or by careful diet.
It can be monitored using clinistix or blood/urine analysis
Until the discovery of insulin in 1922 by Banting and Best, diabetes was an untreatable, fatal disease.
Create 2 true or false questions and add them to the spreadsheet
6.6 Hormones, homeostasis and reproduction
Become a diabetes expert and research 4 facts about
6.6.A1 Causes and treatment of Type I and Type II diabetes.
6.6 Hormones, homeostasis and reproduction
6.6.U2 Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature.
Secreted by: thyroid gland
Targets: most body cells
Effects:
6.6 Hormones, homeostasis and reproduction
6.6.U2 Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature.
6.6 Hormones, homeostasis and reproduction
How is thyroxine regulated?
6.6.U2 Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature.
6.6 Hormones, homeostasis and reproduction
Too much or Too Little
6.6.U2 Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature.
6.6 Hormones, homeostasis and reproduction
6.6.U3 Leptin is secreted by cells in adipose tissue and acts on the hypothalamus of the brain to inhibit appetite.
Produced by: adipose cells (fat storage cells)
Targets: appetite control centre of the hypothalamus (in brain)
Effects:
An increase in adipose tissue increases leptin secretions into the blood, causing appetite inhibition and hence reduced food intake.
6.6 Hormones, homeostasis and reproduction
How does leptin work?
When we starve, fat cells shrink and the amount of stored energy decreases.
This reduces the amount of leptin released
Our brain detects this and stimulates the vagus nerve.
This nerve tells us we are hungry and so we eat more!
This increases our fat stores and in response the amount of leptin produced. So we stop eating!
6.6 Hormones, homeostasis and reproduction
The brains of obese people are resistant to leptin.
Because they have a lot of stored fat, they produce a lot of leptin.
But their brain does not respond to it and keeps stimulating the vagus nerve.
So they always feel hungry and keep eating.
This makes them fatter!
6.6 Hormones, homeostasis and reproduction
These mice could not produce leptin
When they had leptin injected into them, they were healthy
When they had leptin injected into them, they did not respond to the signal
These mice could not recognise leptin
6.6 Hormones, homeostasis and reproduction
Describe how leptin is involved in controlling the appetite (3)
Outline how the human body prevents blood glucose concentration from rising excessively (5)
Secreted by adipose/fat storage tissue/cells;
Transported in blood;
(Target organ) is the hypothalamus;
Suppresses appetite/reduces food intake
6.6 Hormones, homeostasis and reproduction
blood glucose concentration monitored by pancreas/islets/beta cells;
(more) insulin secreted in response to high blood glucose / glucose above threshold level;
insulin stimulates cells to absorb glucose;
glucose used in cell respiration (rather than lipids);
glucose converted to glycogen;
by liver/muscle cells;
glucose converted to fatty acids / triglycerides / fat;
negative feedback process;
Accept points if in a clearly annotated diagram.
6.6 Hormones, homeostasis and reproduction
What are the causes of type I and type II diabetes?
| Type I | Type II |
A. | autoimmune disease leading to reduced insulin secretion | decreased responsiveness of the body to insulin |
B. | decreased responsiveness of the body to insulin | autoimmune disease leading to reduced insulin secretion |
C. | increased responsiveness of the body to insulin | autoimmune disease leading to increased insulin secretion |
D. | autoimmune disease leading to increased insulin secretion | increased responsiveness of the body to insulin |
6.6 Hormones, homeostasis and reproduction
6.6 U4 Melatonin is secreted by the pineal gland to control circadian rhythms.
Made by the pineal gland
It controls our sleep and wake cycles
Light affects melatonin levels
When light levels are low more melatonin is secreted
This can result in Seasonal Affective Disorder (SAD)
It can be used to prevent jet lag!
6.6 Hormones, homeostasis and reproduction
Melatonin levels change over 24 hrs
6.6 U4 Melatonin is secreted by the pineal gland to control circadian rhythms.
6.6 Hormones, homeostasis and reproduction
Melatonin secretion changes as we age...
6.6 U4 Melatonin is secreted by the pineal gland to control circadian rhythms.
What does this graph tell us?
6.6 Hormones, homeostasis and reproduction
6.6 Hormones, homeostasis and reproduction
6.6 Hormones, homeostasis and reproduction
6.6.U5 A gene on the Y chromosome causes embryonic gonads to develop as testes and secrete testosterone.
Humans have 23 pairs of chromosomes in diploid somatic cells (n=2).
22 pairs of these are autosomes, which are homologous pairs.
One pair is the sex chromosomes.
XX gives the female gender, XY gives male.
The X chromosome is much larger than the Y.
X carries many genes in the non-homologous region which are not present on Y.
The presence and expression of the (Sex Determining Region Y) SRY gene on Y leads to male development.
SRY
6.6 Hormones, homeostasis and reproduction
SRY
In embryos the first appearance of the gonads is essentially the same in the two sexes. Gonads could become either ovaries or testes.
If present the SRY gene encodes for a protein known as testis determining factor (TDF). TDF is a DNA binding protein which acts as a transcription factor promoting the expression of other genes.
In the presence of TDF the gonads become testis. In the absence of TDF the gonads become ovaries and the developing fetus becomes female.
6.6 Hormones, homeostasis and reproduction
Testosterone
6.6.U6 Testosterone causes pre-natal development of male genitalia and both sperm production and development of male secondary sexual characteristics during puberty.
The testes develop from the embryonic gonads when the the embryo is becoming a fetus (30mm long, eighth week of pregnancy).
The testes secrete testosterone which causes the male genitalia to develop.
At puberty the secretion of testosterone increases causing:
6.6 Hormones, homeostasis and reproduction
Oestrogen and progesterone
6.6.U7 Estrogen and progesterone cause pre-natal development of female reproductive organs and female secondary sexual characteristics during puberty.
At puberty the secretion of estrogen and progesterone increases causing:
Oestrogen and progesterone are present. At first they are secreted by the first by the mother’s ovaries and later by her placenta.
In the absence of fetal testosterone and the presence of maternal oestrogen and progesterone, female reproductive organs develop (ovaries develop from the embryonic gonads) due to:
6.6 Hormones, homeostasis and reproduction
The female external reproductive organs
6.6 Hormones, homeostasis and reproduction
6.6.S1 Annotate diagrams of the male and female reproductive system to show names of structures and their functions.
Oviduct (Fallopian Tube)
Ovary
Uterus
Cervix
Bladder
Urethra
Vagina
The female reproductive organs
Challenge: Where do women pass their urine?
6.6 Hormones, homeostasis and reproduction
6.6.S1 Annotate diagrams of the male and female reproductive system to show names of structures and their functions.
The female reproductive organs
6.6 Hormones, homeostasis and reproduction
6.6.S1 Annotate diagrams of the male and female reproductive system to show names of structures and their functions.
Label the male reproductive organs
Bladder
Prostate Gland
Sperm Duct
Urethra
Testes
Scrotum
Penis
6.6 Hormones, homeostasis and reproduction
6.6.S1 Annotate diagrams of the male and female reproductive system to show names of structures and their functions.
Seminal Vesicle
6.6 Hormones, homeostasis and reproduction
Can you label and annotate the diagram of the female reproductive system?
6.6.S1 Annotate diagrams of the male and female reproductive system to show names of structures and their functions.
6.6 Hormones, homeostasis and reproduction
6.6.S1 Annotate diagrams of the male and female reproductive system to show names of structures and their functions.
| a. uterus |
| |
b. fallopian tube (oviduct) | |
| |
c. ovary | |
| |
d. endometrium (lining of the uterus) | |
| |
e. cervix | f. vagina |
|
|
g. kidney | h. ureter |
i. bladder | j. urethra |
6.6 Hormones, homeostasis and reproduction
6.6.S1 Annotate diagrams of the male and female reproductive system to show names of structures and their functions.
6.6 Hormones, homeostasis and reproduction
6.6.S1 Annotate diagrams of the male and female reproductive system to show names of structures and their functions.
| a. Vas deferens (sperm duct) |
| |
b. Prostate gland | |
| |
c. urethra | |
| |
d. Penis/erectile muscle | |
| |
e. Seminal vesicle | f. epididymis |
|
|
g. testis (pl. testes) | h. scrotum |
|
|
6.6 Hormones, homeostasis and reproduction
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones.
6.6 Hormones, homeostasis and reproduction
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones.
6.6 Hormones, homeostasis and reproduction
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones.
6.6 Hormones, homeostasis and reproduction
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones.
uterus lining thickens with blood vessels
menstruation occurs
ovulation occurs
uterus lining breaks down
an egg matures ready for release
egg travels down oviduct (fallopian tube)
egg disintegrates
6.6 Hormones, homeostasis and reproduction
Put these statements in the correct order
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones.
uterus lining thickens with blood vessels
an egg matures ready for release
ovulation occurs
egg travels down oviduct (fallopian tube)
egg disintegrates
uterus lining breaks down
menstruation occurs
6.6 Hormones, homeostasis and reproduction
Put these statements in the correct order - Answers
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones.
Gonadotropin Releasing Hormones (GnRH)
Hypothalamus
Pituitary
Follicle Stimulating Hormones (FSH)
Primary Oocyte
Secondary Oocyte
Oestrogen
Lutenising Hormone (LH)
Follicular
Luteal
Progesterone
Negative Feedback
Positive Feedback
6.6 Hormones, homeostasis and reproduction
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones.
6.6 Hormones, homeostasis and reproduction
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones.
6.6 Hormones, homeostasis and reproduction
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones.
Gonadotropin Releasing Hormones (GnRH) released from hypothalamus
6.6 Hormones, homeostasis and reproduction
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones.
Triggers FSH from ant. Pituitary gland
Primary Oocyte matures to form Secondary Oocyte
As it matures, it releases oestrogen
Oestrogen – 1. inhibits FSH
2. Inhibits LH (low concentrations of Oestrogen – negative feedback)
Approx 10 days - Oestrogen levels rise
High Oestrogen levels cause lutenising hormone release
LH increase causes follicle to ovulate (ovulation)
6.6 Hormones, homeostasis and reproduction
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones.
Follicle forms corpus luteum
Corpus luteum releases and oestrogen and progesterone
This prepares the endometrium for the potential of pregnancy after ovulation. It triggers the lining to thicken to accept a fertilized egg. It also prohibits the muscle contractions in the uterus that would cause the body to reject an egg
Implantation
Oestrogen and Progesterone levels inhibit GnRH, FSH and LH
Menstruation
Oestrogen and Progesterone levels inhibit drop. The endometrium lining breaks down.
6.6 Hormones, homeostasis and reproduction
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones.
6.6 Hormones, homeostasis and reproduction
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones.
6.6 Hormones, homeostasis and reproduction
FSH (Follicle stimulating hormone)
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones.
6.6 Hormones, homeostasis and reproduction
LH (luteinizing hormone)
6.6.U8 The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones.
6.6 Hormones, homeostasis and reproduction
Oestrogen
6.6 Hormones, homeostasis and reproduction
Progesterone
6.6 Hormones, homeostasis and reproduction
More Menstrual Cycle Animations
How does the contraceptive pill work?
6.6 Hormones, homeostasis and reproduction
Key Hormones in IB Biology
Insulin
Thyroxin
Leptin
Melatonin
FSH
LH
Estrogen
Progesterone
Testosterone
Pre-natal development of male genitalia, sperm production, development of male secondary sexual characteristics during puberty.
Lowers blood glucose concentration – converts glucose to glycogen for storage in the liver
Raises blood glucose concentration – converts glycogen, in the liver, to glucose
Glucagon
inhibits appetite
Regulates the metabolic rate and helps to control body temperature
controls circadian rhythms
Pre-natal development of female reproductive organs and female secondary sexual characteristics during puberty. Causes the uterine lining to thicken.
Pre-natal development of female reproductive organs and female secondary sexual characteristics during puberty. Maintains the lining of the uterus.
Stimulates the growth and development of ovarian follicles (bodies containing eggs).
Triggers ovulation, the release of the oocyte (egg) from the ovary
6.6 Hormones, homeostasis and reproduction
Explain the role of hormones in the regulation of the menstrual cycle (8 Marks)
FSH and LH are produced by the pituitary gland;
estrogen and progestin are produced by the ovary;
FSH stimulates the ovary to promote development of a follicle;
The developing follicles secrete estrogen, which inhibits FSH (negative feedback);
Oestrogen stimulates growth of endometrium;
Oestrogen stimulates LH secretion (positive feedback);
LH stimulates follicle growth and triggers ovulation;
(the secondary oocyte leaves the ovary and) follicle becomes corpus luteum;
The corpus luteum secretes estrogen and progesterone;
Estrogen and progesterone maintain the endometrium;
Estrogen and progesterone inhibit LH and FSH (negative feedback);
After (two weeks) the corpus luteum degenerates progesterone and estrogen levels fall;
This triggers menstrual bleeding, the loss of endometrium;
The pituitary gland secreted FSH and LH, as they are no longer inhibited (and the menstrual cycle continues);
May credit marks that are clearly drawn and correctly labelled on diagrams or flow charts
6.6 Hormones, homeostasis and reproduction
IVF is often used to overcome infertility caused by blocked Fallopian tubes.
On the right is a special x-ray called a hydrosalpingogram.
A dye is infused through the cervix into the uterus and from there it flows through the fallopian tubes and into the pelvic cavity.
This woman is all clear, you can see the swirls of dye coming out the ends of her tubes
Uterus
Tube administering dye via vagina
Fallopian tube filled with dye
Dye in the pelvic cavity
6.6 Hormones, homeostasis and reproduction
Other causes of infertility:
Female:
Male
6.6 Hormones, homeostasis and reproduction
6.6 Hormones, homeostasis and reproduction
Sumamrise this information in 5 sentences or less
6.6.A4 The use in IVF of drugs to suspend the normal secretion of hormones, followed by the use of artificial doses of hormones to induce superovulation and establish a pregnancy.
For approximately two weeks before implantation the woman takes progesterone (which maintains the endometrium), usually in the form of a suppository, to aid implantation. This treatment is continued until pregnancy test, and if positive, until 12 weeks of gestation.
As the natural success rate of implantation is around 40% usually two or three blastocysts (growing fertilised egg) are implanted. As a consequence the chances of IVF treatment leading to multiple pregnancies are high.
Down-regulation is the first step in IVF is the shutting down of the menstrual cycle, by stopping secretion of the pituitary and ovarian hormones. The process takes about two weeks and allows better control of superovulation. Down-regulation is done with a drug, commonly in the form of a nasal spray.
Next superovulation collects multiple eggs from the woman. High doses of FSH are injected over approximately a ten day period to stimulate the development of multiple follicles (the developing egg and their surrounding cells). When follicles reach 15-20mm in diameter an injection of HCG is given to start maturation process. Approximately 36 hours later, under a general anesthetic, follicles (typically 8 – 12) are collected from the ovaries.
Prepared eggs (removed from the follicles) are combined with sperm in sterile conditions. Successfully fertilised eggs are then incubated before implantation.
6.6 Hormones, homeostasis and reproduction
What did Harvey do?
6.6.A5 William Harvey’s investigation of sexual reproduction in deer.
Harvey studied animal reproduction, particularly in chickens and deer. He dissected female deer after mating to observe changes in the sexual organs and found none.
‘seed and soil’ theory of Aristotle states that the male produces a seed which forms an egg when mixed with menstrual blood. The egg then develops into a fetus inside the mother.
Harvey came to understand that menstrual blood did not contribute to the formation of a fetus (true), putting Aristotle's idea to rest.
He also questioned the direct role of semen in reproduction (false).
His biggest problem was that without microscopes (invented 17 years after his death) that sperm, eggs and embryos are too small to observe.
His findings, both true and false, are based on a misinterpretation of insufficient data.
6.6 Hormones, homeostasis and reproduction
What did Harvey do?
6.6.A5 William Harvey’s investigation of sexual reproduction in deer.