Class Notes (809,120)
Canada (493,535)
Biology (2,220)
BIO270H1 (61)


10 Pages
Unlock Document

University of Toronto St. George
Chris Garside

Lecture 6: Reproduction: Two strategies for reproduction  K-Type Strategists: i. Few offspring ii. A lot of care for offspring iii. Delay further reproduction so parent can tolerate cost of nurturing  R-Type Strategists: i. Rapid reproduction ii. Many offspring iii. Little or no care provided  Rabbits: both R and K type, many offspring and rapid, but provide care. Reproductive cycles:  Semelparous: reproduces once, dies after: Pacific Salmon  Iterparous: multiple reproductive cycles: Atlantic Salmon Gametogenesis: production of gamets: sex cells  Spermatogenesis: Spermatozoa: Testis  Oogenesis: Ova: Ovaries Gonads: tissue that produces gametes Variations in Reproduction (variation for evolution) o Gametogenesis: genome of different combination of chromosomes. o Meiosis: chromosomal recombination o Fertilization: unique combination of ova and spermatozoa Reproductive Hormones: - Regulated by positive and negative feedback - Efficacy: influenced by hormone receptor sunthesis - Hormones are the same in both males and females Steroid Hormones: * They bind to nuclear hormone receptor (NHR)  NHR dimerizes with DNA-binding proteins  Active transcription factor formed  Progestrone: i. Male and female ii. From cholesterol iii. Metabolized to adrostenedione  Androgen: i. Metabolized to androstenedien (Testosterone ii. Precursor for estrogen synthesis (EstrogenEstrone+ Estradiol 17 Gonadotropins: (nonsteroidal) - Produced in anterior pituitary - Controls steroid synthesis - Taxa specific - Regulated by: Gonadotropin-Releasing Hormone (GnRH) a. Produced by hypothalamic neurons b. Released into portal system to the anterior pituitary  Follicle-Stimulating Hormone (FSH) i. Composed of and ii. Hertodimer iii. Modified by glycosalation iv. Produced on demand v. Stimulates: spermatogenesis and follicle ripening  Lutenizing Hormone (LH) i. Induces production of testosterone by interstitial cells of testes ii. Induces follicle to produce estrogens iii. Stored and Released Sex Determinism: *Mammals: Y chromosome is sex determining for males *Birds/Butterflies: W chromosome is sex determining for females *Others: not genotype determined: haplo-diploidy: i. fertilized diploid: female ii. unfertilized haploid: male *Temperature-Dependent Sex determination  Pivotal Temperature: Equal number of males and females Asexual Reproduction *Advbantageous for animals in stable environment  Clones: coral i. Buds form from somatic tissue ii. Single individual produces colony  Parthenogenesis: i. Only ova (unfertilized embryo makes organism) ii. No male gamete required Oogenesis: 3 types:  Ovipary: i. Ova expelled ii. External development  Vivipary i. Internal fertilization ii. Internal development  Ovivipary i. Internal fertilization ii. Internal development: nutrient source is yolk Reproduction - Meiotic division II: post-poned till puberty - Granulose Cells: Somatic Follicle cells - Proliferation of granulose: secretes ECM, zona pellucida formed (separates from oocyte) - there are - Cytoplasmic bridges between oocyte and granulose cells so the cells can provide nutrients - Theca: layer of connective tissue which produce androgens Egg Structure:  Aquatic: i. Permeable to water ii. Gelatinous with viscous coating iii. Unfertilized, develop externally once fertilized iv. No shell: external fertilization possible v. Limitation: requires aquatic environment  Terrestrial: i. Resist dehydration ii. Hardened CaCO3 shell iii. Limitation: internal fertilization  Placental (Eutherian) and Marsupial (Metatherian): i. No eggshell ii. Internal rearing (safer) iii. Enclosed in amnion Extraembryonic membrane of Amntiotes:  Amnion i. Surrounds embryo ii. Encloses fluid (cushion) iii. Favorable ionic/osmotic environment  Shell
More Less

Related notes for BIO270H1

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.