Life History Ch 5 PDF

Life History – the process from embryo to death Stages Embryony → maturation → senescence (fancy word for dying) Ontogeny – embryonic development; from fertilization to birth/hatching Maturation – from birth to sexual maturity (includes growth and learned skills) Abrupt changes a...

Life History – the process from embryo to death Stages Embryony → maturation → senescence (fancy word for dying) Ontogeny – embryonic development; from fertilization to birth/hatching Maturation – from birth to sexual maturity (includes growth and learned skills) Abrupt changes are labeled as metamorphosis Senescence – aging; loss of vigor and reproductive ability Fig. 5.1 Early in development (Kardong page 163) Cells of embryo sort into three germ layers: Ectoderm, endoderm, mesoderm Each of these three layers will be specific regions that give rise to body organs Similar steps of embryonic development are accepted as evidence of homology (if you don’t remember homology, look it up please). Question: If we see homology between different species, what can that tell you? Stages in the progression of embryonic development Zygote – cleavage begins Morula Blastula – cleavage ends Gastrula - gastrulation Neurula - neurulation MEMORIZE THESE STAGES AND THEIR ORDER An egg is a cell = cell membrane = cytoplasm = nucleus Yolk The precursor to yolk starts in the liver and is called vitellogenin. It is a transported form of yolk. From the liver it moves to the blood It is carried to the ovary and accumulates in the ovum In the ovum, it is transformed to yolk platelets which are storage packets of nutrients How much yolk is stored depends on the species.  Create a chart for studying that defines and shows (with drawings) the following terms Microlecithal, mesolecithal, and macrolecithal Isolecithal vs. telolecithal And which groups of animals have these Terms to know: Ovarian or follicle cells Corona radiata Cortical granules Zona pellucida – in mammals = Vitelline membrane in all other animals You are responsible for looking up the functions of these structures Cleavage After fertilization, repeated mitotic cell division of the zygote occurs during cleavage. The first cleavage furrows appear at the _________ and progress toward the __________. Holoblastic – what is it and who demonstrates it? Meroblastic – what is it and who demonstrates it? Discoidal – what is it and who demonstrates it? Animal pole –active cytoplasm and contains the nucleus Takeaway – the cleavage process is influenced by the amount of yolk. Vegetal pole – less active cytoplasm and contains the yolk Fig. 5.2  In all chordates cleavage starts with a single-celled zygote and ends in a multicellular, hollow blastula (see previous slide). Variation in the process has to do with the amount of yolk accumulated. Simplest cleavage pattern is in amphioxus ( because very little yolk) Amphibians – have much more yolk than amphioxus Fish, reptiles, birds, and monotremes have large stores of yolk Mammals have very little yolk – why? Gastrulation = gut formation The rearrangement of cells created during cleavage Forming of a gastrocoel (aka archenteron) Occurs simultaneously as neurulation – nerve formation Three germ layers differentiate – ectoderm, mesoderm, endoderm Mesoderm becomes tubular and forms gut As cells move they are positioned so that they can communicate with one another which influences organ formation later. Fig. 5.17 Amphioxus and amphibian gastrulation and neurulation amphioxus amphibian  Parturition – act of giving birth via viviparity Oviposition – act of laying eggs Parition – includes parturition and oviposition