Biology Sylvia S. Mader Michael Windelspecht Chapter 42 Animal Development and Aging Lecture Outline See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes. 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1

Biology, 9th ed, Sylvia Mader Fertilization Chapter 44 Animal Development Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. microvilli of oocyte plasma membrane 2. Acrosomal enzymes digest a portion of zona pellucida. tail 3. Sperm binds to and fuses with oocyte plasma membrane. sperm 1. Sperm makes its way through the corona radiata. corona radiata 4. Sperm nucleus enters cytoplasm of oocyte. 5. Cortical granules release enzymes; zona pellucida becomes fertilization membrane. plasma membrane nucleus middle piece head acrosome fertilization membrane 6. Sperm and egg pronuclei are enclosed in a nuclear envelope. cortical granule sperm pronucleus oocyte plasma membrane zona pellucida egg pronucleus © David M. Phillips/Visuals Unlimited; (Chick, p. 779): © Photodisc/Getty Images

Early Developmental Stages Biology, 9th ed, Sylvia Mader Chapter 44 Early Developmental Stages Animal Development Development – all changes that occur during the life cycle First stages of development, organism is called an embryo After fertilization, the zygote undergoes cleavage Cleavage is cell division without growth Morula forms a blastula with a hollow blastocoel

Cleavage Note: Size is not increasing

Blastula

Biology, 9th ed, Sylvia Mader Chapter 44 Tissue Development Animal Development Gastrulation – formation of a gastrula Germ layer formation and differentiation Blastopore Pore created by the inward folding of cells Eventually becomes the anus

Biology, 9th ed, Sylvia Mader Chapter 44 Embryonic Germ Layers Animal Development

Biology, 9th ed, Sylvia Mader Chapter 44 Organ Development Animal Development Formation of organs 1st to develop Neural tube Notochord Skeletal rod

Neurulation

Organogenesis of Chick Embryo Rudimentary organs have formed (56 hours) Eye Forebrain Heart Somites Neural Tube

Extraembryonic Membranes Biology, 9th ed, Sylvia Mader Chapter 44 Extraembryonic Membranes Animal Development Chorion –Gas exchange Amnion –Fluid filled Allantois – collects nitrogenous wastes (umbilical cord) Yolk sac – provides nourishment Presence of embryonic membranes in humans demonstrates our evolutionary relationship to reptiles

Extraembryonic Membranes Biology, 9th ed, Sylvia Mader Chapter 44 Extraembryonic Membranes Animal Development Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. embryo allantois amnion yolk sac chorion Chick embryo chorion amnion allantois umbilical cord yolk sac fetal portion of placenta maternal portion of placenta Human

Biology, 9th ed, Sylvia Mader Chapter 44 Placenta Animal Development Mammalian structure that functions in gas, nutrient, and waste exchange between embryonic &maternal cardiovascular systems. Begins formation once the embryo is fully planted

Three Stages of Parturition Biology, 9th ed, Sylvia Mader Chapter 44 Three Stages of Parturition Animal Development Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ruptured amniotic sac a. First stage of birth: cervix dilates placenta b. Second stage of birth: baby emerges placenta uterus umbilical cord c. Third stage of birth: expelling afterbirth

Stem Cells: Undifferentiated Cells

42.2 Developmental Processes Biology, 9th ed, Sylvia Mader Chapter 44 42.2 Developmental Processes Animal Development Development requires: Growth Cellular Differentiation Cells become specialized in structure and function Morphogenesis Produces the shape and form of the body Includes pattern formation Arrangement of tissues and organs within the body Involves apoptosis

Morphogenesis & Changes in Cell Shape

Major Stages of Embryogenesis

Developmental Processes Biology, 9th ed, Sylvia Mader Chapter 44 Developmental Processes Animal Development Cellular Differentiation The zygote is totipotent Cellular Differentiation (continued) Cytoplasmic Segregation Maternal determinants are parceled out during mitosis Cytoplasm of a frog’s egg is not uniform

Cytoplasmic Segregation Biology, 9th ed, Sylvia Mader Chapter 44 Cytoplasmic Segregation Animal Development Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. maternal determinants Cytoplasmic segregation

Biology, 9th ed, Sylvia Mader Chapter 44 Induction Animal Development The ability of one embryonic tissue to influence the development of another tissue Molecular concentration gradients may act as chemical signals to induce germ layer differentiation Developmental path of cells is influenced by neighboring cells

Cytoplasmic Influence on Development Biology, 9th ed, Sylvia Mader Chapter 44 Cytoplasmic Influence on Development Animal Development Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. animal pole Dorsal plane of first division gray crescent Anterior site of sperm fusion Posterior Ventral vegetal pole Dorsal Anterior V entral Posterior a. Zygote of a frog is polar and has axes. b. Each cell receives a part of the gray crescent c. Only the cell on the left receives the gray crescent

Determination & Differentiation

Pattern Formation in Drosophila Biology, 9th ed, Sylvia Mader Chapter 44 Pattern Formation in Drosophila Animal Development Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. Hox-2 mouse chromosomes Hox-1 Hox-3 Hox-4 fly chromosome mouse embryo fruit fly embryo b. mouse fruit fly Courtesy E.B. Lewis

Apoptosis: programmed cell death

Developmental Processes Biology, 9th ed, Sylvia Mader Chapter 44 Developmental Processes Animal Development Homeotic Genes control pattern formation Organization of differentiated cells into specific three-dimensional structures In Drosophila, certain genes control whether a particular segment will bear antennae, legs, or wings Homeotic genes all contain the same particular sequence of nucleotides, the homeobox, that encodes a 60-amino-acid sequence called a homeodomain

How does this happen?