Reproduction

Asexual Reproduction- not just plants

  • usually completely mitotic cell division→cloning

  • can happen in invertebrates

  • faster than finding a mate and doing all that

  • no genetic variation→ all offspring survive in some environments, or they all don’t

  1. fission- division, genetically identical (sea anemone)

  2. budding- new individual grows from existing (hydra)

  3. fragmentation + regeneration- new individual from part of individual (some species of sea star)

Parthenogenesis:

  • species that usually reproduce via sexual reproduction

  • some species all female but 1 individual takes on a male-like role and induces ovulation

  • sometimes produce haploid, unfertilized egs

  • komodo dragons, whiptail lizards, some sharks

  • possible in vertebrates and invertebrates

  • creates female offspring

Sexual Reproduction

  • haploid gamete + haploid gamete → chromosome reduction results from meiosis

  • lots of diversity

  • Non-humans- hermaphrodites→ testes+ovary (Ex: earthworms, typically do still mate w/ others, both can exchange sperm and carry offspring)

  • Sex reversal (Bluehead wrasse, when there is a shortage of males, females become sperm producer)

Haplodiploidy

  • haploid male vs diploid female

  • hymenoptera do this, but some groups too (honeybees, ants, wasps)

  • reproduce sexually to get daughters or asexually to get sons

External Fertilization

  • eggs and sperm released into environment

  • usually aquatic environment

  • spawning- groups of eggs and sperm producers of the same species release gametes at same time + location

Internal Fertilization

  • requires a more complex reproductive system

  • behavior b/w 2 sex functions

Zygote Survival

  • survival varies greatly based on # eggs fertilized, size of eggs/offspring, anatomical protection, behavioral protection, parental care

Human Reproductive Organs

  • Female gonads = ovaries, flank the uterus

    • Clitoris = same undifferentiated tissue as in penis, erectile

    • Ovary - follicle matures→ produces estradiol→ expels egg during ovulation, typically one ovary at a time

    • Corpus luteum develops from former follicle and produces estradiol and progesterone

    • Follicle contains oocyte (egg arrested in development)

    • Females born w/ 1-2 million follicles, typically 500 will mature in lifespan

    • Oviduct/Fallopian Tube- egg travels down via cilia and contraction, fertilized egg implants in uterus

    • progesterone keeps uterine lining intact during pregnancy

    • pregnancy tests detect hCG

  • Male gonads = accessory glands + ducts, produce sperm

    • external = scrotum and penis

    • Testes in scrotum is 2 degrees colder than rest of body

    • Sertoli cells in seminiferous tubules = site of sperm formation b/c best in cold temperatures