1/9/2013 Topic 4: Comparative Development What is development? Transformations that an organism undergoes from What is development? single cell to death (also ontogeny) What are the major stages of development? Free living and embryonic parts of life cycle Gametogenesis to Cleavage How we get from one cell to a complex organism Gastrulation & Neurulation Indirect versus direct development Human development and extra-embryonic structures Organogenesis Growth & Maturation What are some examples of organogenesis? gametogenesis Eye Development Pharyngeal development Free Living Ontogeny Stages of Development – What are the stages of development? Gametogenesis: Cellular Specialization Spermatogonium2N Oogonium ____________________ _______________ Pre-meiotic Produces spermatozoa Rather unspecialized ______________ duplication Acrosome with species Cortical cytoplasm Oogenesis recognition molecules involved in fertilization 1o spermatocyte 4N 1o oocyte Spermatogenesis Nucleus Two genomes (nuclear & mitochondrial) Meiosis I Neck with mitochondria 2 parts 2o oocyte recombination Tail for locomotion Meiosis 2o spermatocytes 1st polar Cellular 2N body specialization Meiosis II sister chromatids separate Diploid to haploid 4 spermatids 1N Spermiogenesis 1 ovum + 3 polar bodies 4 spermatozoa Liem et al. 2001, Fig 4-6 Liem et al. 2001, Fig 4-7 Stages of Development - Fertilization Stages of Development - _______ _____________________ Outer jelly coat swells in Acrosome + Cortical Granules amphibians Sperm nucleus drawn in Zygote formed Cell division to form a Primary egg cell membrane fertilization blastula membrane 1 cell to ball of cells Perivitelline space created Fertilized Ovum = Zygote to hollow ball of cells Cells are blastomeres Space inside is blastocoel __________ becomes an __________ Newly Ovulated Ovum Liem et al. 2001, Fig 4-8 Liem et al. 2001, Fig 4-10A 1 1/9/2013 Stages of Development - Cleavage Stages of Development - ____________ Cleavage depends on Amphioxus Frog Chicken the amount of yolk in the egg Cells move to form ________________ Little Yolk Ectoderm Cleavage equal & holoblastic Epidermal Neural More Yolk Mesoderm Cleavege unequal & Chondramesoderm holoblastic Endoderm Lots of Yolk This is a “fate map” of a blastula Cleavage meroblastic Liem et al. 2001, Fig 4-10 Liem et al. 2001, Fig 4-11A Stages of Development - Gastrulation Stages of Development - Gastrulation Amphioxus Frog Chicken Gastrulation occurs by _____________ different mechanisms shrinks in different species _____________ _________________ is formed (Cephalochordates) Archenteron will become gut _________________ (Amphibians) Opening to _________________ archenteron is (Birds) blastopore Blastopore will Related partly to become anus amount of yolk Liem et al. 2001, Fig 4-12 Vertebrate Life Fig 3-1 Stages of Development - ___________ Stages of Development Gastrula neurula Zygote Neural plate forms Invagination to give Cleavage neural folds Fusion into neural Blastula tube Gastrulation _________________ Some nerves Pigment cells Gastrula Some cranial bones Some endocrine Neurulation cells Neurula Liem et al. 2001, Fig 4-15 Liem et al. 2001; Vertebrate Life Fig 3-1 2 1/9/2013 Extraembryonic Membranes Early Stages of Human Development Why might mammals be different Extraembryonic from a chicken or frog? Ectoderm ____________ mesoderm Cleavage produces a _________ ____________ mesoderm Outer __________________ Endoderm Homologous to extraembryonic ectoderm Produce extraembryonic structures Inner __________________ Ectoderm + Somatic Mesoderm Gives rise to the embryo, termed the fetus _______ Protect embryo _______ } ____________________ Contains allantois & yolk sac Endoderm + Splanchnic Mesoderm Connects embryo to trophoblast _____________ – Contains yolk Becomes umbilical cord _____________ – Receives waste Liem et al. 2001, Fig 4-17 Liem et al. 2001, Fig 4-18A,B Early Stages of Human Development Stages of Development - _____________ The formation of organs and organ systems _________________ Close contact between embryo and uterus Much of development Formation of a _________ Very complicated Made of both embryonic A separate course! and maternal tissue Very little yolk Germ layers subdivide and Gas Exchange, nutrient give rise to other delivery & waste removal structures Use a flow chart to learn development Photo © MA Hill Liem et al. 2001, Fig 4-16B 3 1/9/2013 See Liem et al. 2001, Table 4-1 for a similar table Vertebrate Life, fig 3-2 1 1/9/2013 Stage of Development – A Closer Look at Organogensis: Growth & Maturation Eye Development and Induction Postnatal stages of development 1. Evagination of optic vesicle 2. Induction of lens placode by optic vesicle Scaling 1 2 3. Invagination to optic cup Increases in size Changes in proportions 4. Invagination to lens cup Next Lecture 5. Pinching off of lens vesicle 6. Lens vesicle induces cornea Sexual maturation 7 7. Formation of pigmented Completion of gonadal 3 4 8 5 6 and neural retinas development 8. Neural retina induces lens Secondary sexual characteristics © Krempel; www.advancedaquarist.com See Liem et al. Fig 4-20 A Closer Look at Organogenesis: Development of the Pharynx A complex structure arising from all germ layers Liem et al. 2001, Fig 4-36 1.