Lecture_27_Reproduction_Lecture 2.pptx

GENERAL BIOLOGY II Lecture 26: Reproduction & Development Chapter: 43 Student Evaluations Please be constructive with your criticism. The Evolution of Reproduction The Evolution of Reproduction Asexual Reproduction Sexual Reproduction The Evolution of Reproduction Asexual Reproduction Produces clone...

GENERAL BIOLOGY II Lecture 26: Reproduction & Development Chapter: 43 Student Evaluations Please be constructive with your criticism. The Evolution of Reproduction The Evolution of Reproduction Asexual Reproduction Sexual Reproduction The Evolution of Reproduction Asexual Reproduction Produces clones Binary fission Budding Fragmentation Parthenogenesis The Evolution of Reproduction Sexual Reproduction Uses meiotic cell division & fertilization Meiosis – halves the number of chromosomes; produces gametes (or spores) Fertilization – combines two gametes to create a diploid zygote The Evolution of Reproduction Sexual Reproduction Many species produce two kinds of gametes Spermatozoa (or Sperm) Ova (or Eggs) Fusion of gametes results in a zygote that grows into an embryo The Evolution of Reproduction Many animals use both sexual and asexual reproduction. What would make an animal favor sexual or asexual reproduction at a particular point in time? The Evolution of Reproduction The Evolution of Reproduction Two-fold cost of sex  Time and energy to find a mate  Fewer offspring per reproductive cycle The Evolution of Reproduction We do not see many organisms that only reproduce asexually in the animal kingdom. Why do you think that is? The Evolution of Reproduction Hypotheses as to why asexual reproduction is not ubiquitous:  Beneficial mutations can be spread through the population via sex  Harmful mutations can be purged via sex  Red Queen Hypothesis Vertebrate Reproduction Vertebrate Reproduction Aquatic vertebrates (fish & amphibians) Use external fertilization  May broadcast spawn  May come close together to increase the chance of fertilization Vertebrate Reproduction Terrestrial vertebrates (reptiles, birds, mammals) Use internal fertilization  Also used by some aquatic animals  Adaptation to reproduction outside of water, the amniotic egg, or increased chance of fertilization Reproductive Strategies r-strategists vs k-strategists Number of offspring vs Parental investment Amniotic Egg Evolved to allow terrestrial animals to lay eggs outside of water Reproductive methods: Oviparity – lay eggs Ovoviviparity – internal egg hatching Viviparity – live birth Mammals use a placenta Male Gametes Produced in the testes Anatomy Head Acrosome – contains enzymes that can penetrate the outer coating of the egg Neck Mostly contains mitochondria Tail Flagellum used for locomotion Female Gametes Eggs Produced in the ovaries Travels through the oviduct (or fallopian tube) Where fertilization usually occurs Fertilized ovum implants in the wall of the uterus to develop Hormone Control of the Reproductive System Hypothalamus releases gonadotropin-releasing hormone Trigger the release of: Luteinizing hormone (LH) Follicle-stimulating hormone (FSH) LH and FSH trigger the release of testosterone, estrogen, and progesterone Hormone Control of the Reproductive System Testosterone and estrogen control the development of secondary sexual characteristics Estrogen and progesterone control the menstrual cycle in females Hormone Control of the Reproductive System When women attain a postreproductive age, menopause results from a decrease of estradiol and progesterone from the ovaries Most non-human placental mammals have an estrus cycle during which females are reproductively receptive. This generally occurs less frequently than in primates. Reproductive Development Gametogenesis – formation of gametes Spermatogenesis – formation of sperm Oogenesis – formation of ova (or eggs) Reproductive Development Sperm is introduced into the female reproductive tract during coitus In the female reproductive tract, sperm undergo capacitation  Increase motility  Loss of membrane proteins  Change in plasma membrane fluidity Reproductive Development After fertilization, the oocyte completes meiosis II, and undergoes changes that prevent polyspermy – fertilization by more than one sperm  Changes to the zygote membrane to become impassable to sperm Reproductive Development Single-celled zygote then divides by mitosis (Cleavage) Increase the number of cells, but not the embryo size Reproductive Development Morula – solid ball of cells Blastula – fluid-filled ball of cells Implantation marks the beginning of Pregnancy Reproductive Development Towards the end of the first trimester, the embryo grows into a fetus The inner cell mass of the blastocyst becomes the embryo, and the outer cell mass becomes the placenta Reproductive Development The blastocyst grows into a bilaminar embryo, and that undergoes Gastrulation, during which the three germ layers are formed Ectoderm Mesoderm Endoderm Reproductive Development The trilaminar embryo then undergoes Organogenesis, during which the organs are formed Reproductive Development Trimesters 2 and 3 are primarily characterized by fetal growth. The doubles in size during the last two months of gestation. Finally, childbirth ensues, and is shortly followed by the delivery of the placenta. For Next Class Complete the Quiz on CANVAS Read The rest of Chapter 42: The Immune System