More than one may be true

AP Biology 2005-2006

More than one may be true 1. A cell contains two homologous sets

of chromosomes. a. The cell that contains these homologous

sets of chromosomes must be diploid. b. Each homologous pair of chromosomes

was formed by DNA replication of a single chromosome. c. Barring mutation, the two chromosomes

in a homologous pair must be identical. d. One member of each homologous pair is

from the maternal family line; the other member is from the paternal family line.


Again, each letter is a question

1. Two sister chromatids are joined at the centromere prior to meiosis.

a. These chromatids make up a diploid chromosome. b. The cell that contains these sister chromatids must be

diploid. c. The two sister chromatids were formed by DNA

replication of a single chromatid.


Animal Reproduction

Chapter 46.


Sexual & asexual reproduction Asexual

offspring all have same genes (clones) no variation unless there is mutation

Sexual gametes (sperm & egg) fertilization mixing of genes variation


Parthenogenesis Development of an unfertilized egg

honey bees drones = males produced through

parthenogenesis haploid workers & queens = females produced from

fertilized eggs diploid

queen worker drone


Hermaphrodites

flat worm

earthworms mating

Having functional reproductive system of both sexes


Fertilization Joining of egg & sperm

external usually aquatic animals

internal usually land animals


Development External

development in eggs fish & amphibians in water

soft eggs= exchange across membrane birds & reptiles on land

hard-shell amniotic eggs structures for exchange of food, O2 & waste

sharks & some snakes live births from eggs

Internal placenta

exchange food & waste live birth


Adaptive advantages? What is the adaptive value of each

type of sexual reproduction number of eggs? level of parental of care habitat?


Reproductive hormones Testosterone

from testes functions

sperm production 2° sexual

characteristics

Estrogen from ovaries functions

egg production prepare uterus

for fertilized egg 2° sexual

characteristics

LH &FSH

testesor

ovaries


Sex hormone control in males

Hypothalamus

Pituitary

Testes

Body cells

GnRH

FSH & LH

testosterone


Testicles produces sperm & hormones

Scrotum sac that holds testicles

outside of body Epididymis

where sperm mature Vas deferens

tubes for sperm to travel from testes to penis

Prostate, seminal vesicles, Cowper’s (bulbourethal) glands

nutrient rich fluid to feed & protect sperm

buffer to counteract acids in vagina

Male reproductive system


Male reproductive system

Testes & epididymis sperm production &

maturation

Glands seminal vesicles,

prostate, bulbourethal produce seminal fluid =

nutrient-rich

seminiferous tubule

sperm

spermatocytes


SpermatogenesisEpididymis Testis

Coiledseminiferoustubules

Vas deferens

Cross-section ofseminiferous tubule

Spermatozoa

Spermatids(haploid)

2°spermatocytes

(haploid)

1°spermatocyte

(diploid)

Germ cell (diploid)

MEIOSIS II

MEIOSIS I

AP Biology

Female reproductive system Ovaries

produces eggs & hormones Uterus

nurtures fetus; lining builds up each month

Fallopian tubes tubes for eggs to travel

from ovaries to uterus Cervix

opening to uterus, dilates 10cm (4 inches) for birthing baby

Vagina birth canal for birthing baby

2005-2006


LH

FSH

estrogen

progesterone

lining of uterus

egg development ovulation = egg release

corpus luteum

0 7 14 21 28days

Menstrual cycle

Hypothalamus

Pituitary

Ovaries

Body cells

GnRH

FSH & LH

estrogen


Egg maturation in ovary Corpus luteum

produces progesterone to maintain uterine lining


Female hormones FSH & LH

release from pituitary stimulates egg development & hormone release peak release = release of egg (ovulation)

Estrogen released from ovary cells around developing egg stimulates growth of lining of uterus lowered levels = menstruation

Progesterone released from “corpus luteum” in ovaries

cells that used to take care of developing egg stimulates blood supply to lining of uterus lowered levels = menstruation


Oogenesis

Meiosis 1 completedduring egg maturation

Meiosis 2 completedtriggered by fertilization

ovulation

What is the advantage of this development system?


Fertilization


Fertilization Joining of sperm & egg

sperm head enters egg


Cleavage Repeated mitotic divisions of zygote

1st step to becoming multicellular unequal divisions establishes body plan

different cells receive different portions of egg cytoplasm & therefore different regulatory signals


Cleavage zygote morula blastula

establishes future development


Gastrulation Establish 3 cell layers

ectoderm outer layers

skin, nails, teeth, nerves

mesoderm blood, bone & muscle

endoderm inner lining

digestive system

ectoderm

mesoderm

endoderm


Neurulation 1st organ to form is notochord &

nerve chord develop into nervous system

Neural groove

Notochord

Neural tube


Placenta Materials exchange across membranes


Getting crowded in there!! 32 weeks (8 months)

The fetus sleeps 90-95% of the day & sometimes experiences REM sleep, an indication of dreaming


Birth

Hormone induction

positive feedback


Intestine

Placenta

Umbilicalcord

Wall ofuterus

VaginaCervix

Birth (36 weeks)

Bladder


The end of the journey!


Contraception and Abortion Contraception, the deliberate prevention of

pregnancy, can be achieved in a number of ways

Contraceptive methods fall into three categories: Preventing release of eggs and sperm Keeping sperm and egg apart Preventing implantation of an embryo


You should now be able to:

1. Distinguish between asexual and sexual reproduction

2. Explain how hermaphroditism may be advantageous to animals that have difficulty encountering a member of the opposite sex

3. Describe various ways in which animals may protect developing embryos

4. Using diagrams, identify and state the function of each component of the male and female reproductive systems


5. Describe oogenesis and spermatogenesis; describe three major differences between them

6. Explain how the uterine and ovarian cycles are synchronized and describe the functions of the hormones involved

7. List the various methods of contraception, how each works, and how effective each is

8. Describe techniques that allow us to learn about the health and genetics of a fetus


Documents

More than one may be true