Prenatal Development

Question 1

What are chordates?

Answer 1

All animals with spinal cords

Question 2

What do a majority of these chordates have?

Answer 2

A backbone (vertebral column)

Question 3

What does biodiversity mean?

Answer 3

The number of different kinds of species in each group of living animals

Question 4

Describe the species biodiversity

Answer 4

Other insects and beetles are major groups.
No. of chordates are very small
Estimates of how many species on earth = 5-5- million

Question 5

Describe the similarities of development across species

Answer 5

Diverse species e.g mice + humans = similar gestational processes
all species develop from single eggs, which diversify into complex organisms w/ brains, eyes and mouths.

Question 6

Who suggested the recapitulation theory?

Answer 6

Suggested by Haeckel when reporting the similarity of forms of early embryos of a variety of species

Question 7

What is the recapitulation theory?

Answer 7

Popularised in the 19th century. This theory suggests that embryonic development (ontogeny) repeats the evolutionary history of an animal’s ancestors (phylogeny).

Drawing of embryos supported this theory.

Question 8

How does the recapitulation relate to humans?

Answer 8

Human development occurs in the form of adult animals lower down the evolutionary scale. Animals would stop developing at the appropriate time for their species.

Question 9

What is a problem with the recapitulation theory?

Answer 9

Technological advancement (photography developing in the late 19th century), shows that this view is not correct.

Question 10

What can be said learnt from the recapitulation debate?

Answer 10

1. Prior beliefs = influence perception
2. How reliant science enquiry is on technology

Question 11

Name 3 examples of improvements in molecular biology that caused an increased understanding of development

Answer 11

1950s - invention of the microscope
1695 - performation theory of development
Late 19th century - improvement in optics

Question 12

What is Hartoseker’s Performation theory?

Answer 12

Nicolaas Hartoseker saw a tiny human inside a sperm cell when using a more powerful microscope. This popularised the idea that the womb was an oven where tiny humans expanded.

Question 13

What did the improvement in optics lead to?

Answer 13

Led to embryonic growth now understood to involve substantial differentiation.

Question 14

What did Aristotle suggested about prenatal development that was popularised around 384-322 B.C?

Answer 14

Suggested a chain of being (Scala naturae) where there was higher and lower life forms - a hierarchy. This idea is widespread outside science.

Question 15

What are the problems of Aristotle’s suggestions?

Answer 15

Theory suggested evolutionary change is a directional process = false
Misconception that humans are at the top (the most perfect)

Question 16

What are the three stages of prenatal development?

Answer 16

1. The Geminal Period = conception to implantation in the uterine wall
2. The Period of the Embryo = implantation to ~2mths
3. The Period of the Foetus = 2mths to birth

Question 17

What is the Geminal Period?

Answer 17

1. Sperm and egg cell fuse = zygote (fallopian tube)
2. Zygote moves to uterus
3. In first 4 days, Zygote cells multiply = mass of cells - morula (daughter cells look the same as parent cells)
4. Day 5 = turns into a blastocyst (earliest example of physical differentiation of tissue in the prenatal development )
5. Day 8-9 = implantation of blastocyst on the uterine wall making a hypoblast

Question 18

What is the Period of the Embryo?

Answer 18

1. Blastocyst = 3 layers of major tissues (ectoderm, mesoderm and endoderm)
2. Post implantation = embryo has identifiable diff. tissues e.g heart, eye, cartilaginous scaffolds but not bones
3. One month post-implantation = individual toes, fingers is apparent and gut bulge

Question 19

What is an ectoderm?

Answer 19

When the blastocyst differentiates into the nervous system, teeth, nails and epidermis (outer layer of skin)

Question 20

What is a mesoderm?

Answer 20

When the blastocyst differentiates into muscle, bones, the circulatory and reproductive system

Question 21

What is the endoderm?

Answer 21

When the blastocyst differentiates into the Gastro-intestinal tracts, lungs and glands and systems for excretion and digesting.

Question 22

What is the Period of the Foetus?

Answer 22

2 mths = limbs well formed, brain expanded and foetus can respond to stimulation

4 mths = touch, movement, hearing (20 weeks at gestational age). Foetal bhvr can be talked about from this age.

8mths = genitalia (can be seen), reacts to temp/ painful stimuli/ light, has preferences in position + will reorient self to it.

Question 23

What type of hearing do foetus’ have at 20 weeks gestational age?

Answer 23

Low frequency sounds 250-500 Hz
Normal adults is 20,000 Hz

Babies can’t hear much.

Question 24

What causes a child to vary from typical development?

Answer 24

According to WHO = origins of congenital aberrations are unknown in 50% of cases. They can have genetic or environmental causes.

Genetic example = cystic fibrosis
Environmental experiment = teratogens

Question 25

Compare mitosis and meiosis

Answer 25

Both produce new cells, use DNA replication. They are the 2 kind of cell divisions that happen in the body - producing 2 daughter cells that have the same number as the parent cell.

Question 26

Describe the key points of meiosis

Answer 26

Usually results in gametes containing 23 chromosomes. Each parent gives 23 chromosomes = 46 chromosomes usually

Question 27

What is aneuploidy?

Answer 27

The condition of having fewer or more than 46 chromosomes, 23 pairs

Question 28

How many chromosomes do people w/ Down syndrome have?

Answer 28

47 chromosomes, 21 pairs

Question 29

How many chromosomes do people w/ Edwards syndrome have?

Answer 29

18 pairs = (3 copies of chromosome 18)

Question 30

How many chromosomes do people w/ Patau syndrome have?

Answer 30

3 copies of chromosome 13

Question 31

What are chromosomal variations associated with?

Answer 31

Developmental problems in various organ systems + learning difficulties.

Question 32

True or False? There is variability in how a chromosome may affect a person.

Answer 32

True - sometimes negative affects don't always happen

Question 33

What are the effects of chromosomal variation in sex?

Answer 33

Some, not all = lead to ambiguous genitalia at birth / + some cases = ambiguous secondary sex characteristics at birth. There are more than 2 biological sexes

Question 34

What is Turner syndrome?

Answer 34

45 chromosomes 1:2,000-5,000 Usually appear female = 95%

Question 35

What is Klinefelter syndrome?

Answer 35

48 chromosomes XXXY 1:50,000 Usually appear male until puberty Learning disability often

Question 36

What is a teratogen?

Answer 36

substances that can cause physical or functional defects in the embryo/foetus inside the womb

Question 37

Describe the overall vulnerability of the foetus

Answer 37

At different times of development, diff. developing organs are more/ less vulnerable to teratogens. Examples - Central system = vulnerable throughout - Heart, upper + lower limbs = immune from foetal period - External genitalia = highly vulnerable in foetal period - Spine and brain = highly vulnerable in embryonic period

Question 38

True or False? The mother and foetus shares the same blood supply before the placenta is formed. This makes them vulnerable to teratogenic influences throughout development.

Answer 38

False - The mother and child doesn't share the same blood making them immune to teratogenic influence. When the placenta forms and blood supply is shared, this is when the child becomes vulnerable.

Question 39

Describe the Thalidomide

Answer 39

Thalidomide was developed in 1954 for pregnancy symptoms by the CIBA pharmaceutical company. This only affected children if the drug was prescribed in the first trimester of the pregnancy (misshapen limbs bc highly vulnerable during first trimester).

Question 40

Describe the Thalidomide Tragedy

Answer 40

1. By 1961 = 20,000 children in 46 countries w/ misshapen limbs 2. Cause = people didn't think it was thalidomide bc they didn't understand chemicals can cross the placental barrier 3. Popular idea of cause = widespread testing of atomic bombs pre-1970 in the atmosphere

Question 41

Why was the US not as affected by the Thalidomide Tragedy?

Answer 41

Thalidomide = never approved by the Food + Drug Administration bc of Dr. Frances Oldham Kelsey

Question 42

Describe how many cases there were across countries

Answer 42

Cases of thalidomide poisoning 1. US = ~40 2. UK = ~2,000 3. Germany = ~ 2,500

Question 43

What is foetal alcohol syndrome?

Answer 43

Effects manifests in the developing nervous central = associated w/ neurological problems. It causes problems w/ vision, hearing and learning. It also causes characteristic facial features and microcephaly.

Question 44

Describe DeCasper & Spence (1986)

Answer 44

16 Mothers = gestation ages 7.5 mths pregnant read stories 2x a day When babies = 2.5 days old, played familiar story + new stories in headphones o Group 1 = sucked faster (high amplitude sucking) = familiar story got louder o Group 2 = sucked slower = familiar story got louder Babies = preference for familiar story  shows babies were learning during the womb

Question 45

Describe Harper (1991)

Answer 45

Sampled mothers + babies o Group 1 (learning) = mothers watched neighbors o Group 2 (control) = mothers didn’t watch neighbors Found differences in movement o G1 = ↑ active when soundtrack was played compared to G2

Question 46

Describe James' 2010 review

Answer 46

Fetal learning research is difficult Habituation = decrease to innate behavioural response with repetition = non-association learning o Suggested many studies focusing on habituation learning in children = acoustic stimulation but was more like vibro-acoustic bc it is hard to produce pure acoustic stimulus without vibration Several studies = use exposure to produce data o H/E = methodological limitation = Not randomised, used ‘sham’ or ‘dummy stimulus e.g James et al. 2002