Biology, 9th ed, Sylvia Mader Chapter 44 Chapter 44 Animal Development Animal Development

Early Developmental Stages Outline Early Developmental Stages Fertilization Embryonic Development Effect of Yolk Neurulation and the Nervous System Developmental Process Cellular Differentiation Homeotic Genes Human Embryonic and Fetal Development Fetal Development

Biology, 9th ed, Sylvia Mader Chapter 44 Fertilization Animal Development Fertilization Several sperm penetrate the corona radiata Several sperm attempt to penetrate zona pellucida One sperm enters the egg and their nuclei fuse

Embryonic Development During first stages of development, an organism is called an embryo Following fertilization, zygote undergoes cleavage Morula forms blastula with a hollow blastocoel Germ layers differentiate Ectoderm Mesoderm Endoderm

Lancelet Early Development

Comparative Development of Mesoderm

Neurulation and the Nervous System Develops from midline ectoderm located just above the notochord Thickening of neural plate is seen along dorsal surface of the embryo Neural folds develop on either side of neural groove Neural grove becomes the neural tube

Development of Neural Tube and Coelom in a Frog Embryo

Vertebrate Embryo, Cross Section

Developmental Processes Biology, 9th ed, Sylvia Mader Developmental Processes Chapter 44 Animal Development Development requires: Growth Cellular Differentiation Morphogenesis Adult body cells are totipotent Each contains all the instructions needed by any other specialized cell in the body 3.B.2: Morphogens stimulate cell differentiation and development. Morphogenesis produces shape and form of the body; one of the earliest indications is cell movement; later includes pattern formation (how tissues and organs are arranged in the body).

Cytoplasmic Influence on Development

Induction The ability of one embryonic tissue to influence the development of another tissue Developmental path of cells is influenced by neighboring cells

Control of Nervous System Development

Biology, 9th ed, Sylvia Mader Model Organisms Chapter 44 Animal Development Roundworm, Caenorhabditis elegans Fruit Fly, Drosophila melanogaster Mouse, Mus musculus Fate Maps Show the destiny of each cell as it arises

Development of C. elegans, a Nematode Biology, 9th ed, Sylvia Mader Development of C. elegans, a Nematode Chapter 44 Animal Development 2.E.1: C. elegans development

Development in Drosophila, a Fruit Fly

Biology, 9th ed, Sylvia Mader Homeotic Genes Chapter 44 Animal Development Homeotic Genes control pattern formation Organization of differentiated cells into specific three-dimensional structures 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 Mice and humans have the same four clusters of homeotic genes They are located on four different chromosomes 3.D.2: Morphogens in embryonic development Proteins, called morphogens, form gradients that influence patterns of tissue development. Morphogen gradients turn on genes because they are transcription factors that regulate which genes are active in which parts of the embryo in what order.

Pattern Formation in Drosophila

Extraembryonic Membranes

Human Development Before Implantation

Human Embryonic and Fetal Development Human gestation time - time from conception to birth - approximately nine months Embryonic Development - Months 1-2 Fetal Development - Months 3-9 Extraembryonic Membranes Chorion Amnion Allantois Yolk Sac

Human Embryonic Development

Embryonic Development First Week Morula transformed into blastocyst Gives rise to chorion Second Week Implanting begins Gastrulation occurs Inner cell mass flattened into embryonic disk Ectoderm and Endoderm differentiate

Embryonic Development Third Week Nervous system and circulatory system appear Fourth and Fifth Weeks Umbilical cord is fully formed Limb buds appear Head enlarges Sense organs more apparent

Human Embryo at Beginning of Fifth Week

Embryonic Development Sixth Through Eighth Weeks Head achieves normal relationship with the body Nervous system is developed enough to permit reflex actions

Structure and Function of the Placenta A mammalian structure that exchanges materials between maternal and embryonic circulations Gases Nutrients Wastes

Anatomy of the Placenta in a Fetus at Six to Seven Months

Three Stages of Parturition

Biology, 9th ed, Sylvia Mader Chapter 44 Ending Slide Chapter 44 Animal Development Animal Development