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 Chapter 44 Outline Animal Development 42.1 Early Developmental Stages 42.2 Developmental Processes 42.3 Human Embryonic and Fetal Development 42.4 The Aging Process

42.1 Early Developmental Stages Biology, 9th ed, Sylvia Mader Chapter 44 42.1 Early Developmental Stages Animal Development Fertilization requires that sperm and egg unite to form a zygote Details of Fertilization in Humans A human sperm cell has three parts: The head Contains a haploid nucleus covered by acrosome containing enzymes, allowing the sperm to penetrate the egg. A middle piece Contains ATP‑producing mitochondria The tail A flagellum that allows the sperm to swim

Early Developmental Stages Biology, 9th ed, Sylvia Mader Chapter 44 Early Developmental Stages Animal Development Details of Fertilization in Humans (cont.) An egg Actually a secondary oocyte Surrounded by layers of adhering follicular cells termed the corona radiata Nourish oocyte and follicle Surrounded by the zona pellucida Sandwiched between the plasma membrane of the oocyte and the corona radiata

Early Developmental Stages Biology, 9th ed, Sylvia Mader Chapter 44 Early Developmental Stages Animal Development Details of Fertilization in Humans (cont.) Several hundred sperm reach the oocyte Sperm secrete enzymes to weaken the corona radiata and bind to the zona pellucida Acrosome releases digestive enzymes to allow the sperm to pass through the zona pellucida to the plasma membrane of the oocyte

Early Developmental Stages Biology, 9th ed, Sylvia Mader Chapter 44 Early Developmental Stages Animal Development Details of Fertilization in Humans (cont.) One sperm enters the egg Membrane depolarizes to prevent polyspermy Fertilization membrane forms The secondary oocyte completes meiosis The sperm nucleus releases chromatin A single nuclear envelope surrounds the egg and sperm pronuclei First cell division occurs

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 Embryonic Development Development – all the changes that occur during the life cycle of an organism During first stages of development, an organism is called an embryo Following fertilization, the zygote undergoes cleavage Cleavage is cell division without growth Morula forms a blastula with a hollow blastocoel Appearance of blastula differs between organisms In chickens the blastula resembles a layer of cells spread out over yolk In frogs, the presence of the yolk causes uneven division, forming both an animal and vegetal pole

Lancelet Early Development Biology, 9th ed, Sylvia Mader Lancelet Early Development Chapter 44 Animal Development Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. Zygote Late gastrula mesoderm Morula Cleavage is occurring. blastocoel endoderm ectoderm Gastrulation Is occurring. Early gastrula Blastula ectoderm endoderm blastopore b. archenteron blastocoel (a): © William Jorgensen/Visuals Unlimited

Biology, 9th ed, Sylvia Mader Chapter 44 Chick Blastula Animal Development Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. blastocoel Chick blastula (cross section) yolk (chick): © Photodisc/Getty RF

Early Developmental Stages Biology, 9th ed, Sylvia Mader Chapter 44 Early Developmental Stages Animal Development Tissue Stages of Development Gastrulation – formation of a gastrula Germ layer formation and differentiation Ectoderm – outer layer Mesoderm – middle layer of cells Endoderm – inner layer 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

Comparative Development of Mesoderm Biology, 9th ed, Sylvia Mader Chapter 44 Comparative Development of Mesoderm Animal Development Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. archenteron mesoderm archenteron mesoderm archenteron primitive streak mesoderm ectoderm endoderm ectoderm yolk plug endoderm ectoderm yolk endoderm cross section longitudinal section cross section a. Lancelet late gastrula b. Frog late gastrula c. Chick late gastrula

Early Developmental Stages Biology, 9th ed, Sylvia Mader Chapter 44 Early Developmental Stages Animal Development Organ Stages of Development Nervous system Develops from midline ectoderm located just above the notochord Notochord = dorsal supporting rod 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 Biology, 9th ed, Sylvia Mader Chapter 44 Animal Development Development of Neural Tube and Coelom in a Frog Embryo Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. presumptive neural plate neural groove notochord0 coelom neural tube notochord ectoderm coelom mesoderm gut gut endoderm archenteron notochord yolk a. b. c. d. b: Courtesy Kathryn Tosney

Vertebrate Embryo, Cross Section Biology, 9th ed, Sylvia Mader Chapter 44 Vertebrate Embryo, Cross Section Animal Development Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. neural tube somite notochord gut coelom ectoderm mesoderm endoderm

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 Programmed cell death

Developmental Processes Biology, 9th ed, Sylvia Mader Chapter 44 Developmental Processes Animal Development Cellular Differentiation The zygote is totipotent Has the ability to generate the entire organism Adult body cells lose their totipotency, but do not lose genetic information Each contains all the instructions needed by any other specialized cell in the body

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

Developmental Processes Biology, 9th ed, Sylvia Mader Chapter 44 Developmental Processes Animal Development Cellular Differentiation (continued) Induction and Frog Experiments Induction 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

Development of C. elegans, a Nematode Biology, 9th ed, Sylvia Mader Chapter 44 Animal Development Development of C. elegans, a Nematode Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. egg gonad (8–16 divisions) cuticle (8–11 divisions) gonad vulva (10–13 divisions) cuticle intestine (3–6 divisions) nervous system (6–8 divisions) vulva egg pharynx (9–11 divisions) sperm intestine nervous system pharynx

Developmental Processes Biology, 9th ed, Sylvia Mader Chapter 44 Developmental Processes Animal Development Morphogenesis Process by which an animal achieves its ordered and complex body form Requires that cells associate to form tissues, which give rise to organs Pattern formation Cells of the embryo divide and differentiate, taking up orderly positions in tissues and organs

Developmental Processes Biology, 9th ed, Sylvia Mader Chapter 44 Developmental Processes Animal Development Morphogenesis in Drosophila melanogaster Fruit Fly Pattern formation Embryonic cells express genes differently in graded, periodic, and striped arrangements Anteroposterior polarity is established in the egg before fertilization Gap genes divide the anteroposterior axis into broad regions

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

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

42.3 Human Embryonic and Fetal Development Biology, 9th ed, Sylvia Mader Chapter 44 42.3 Human Embryonic and Fetal Development Animal Development Human gestation time - time from conception to birth - is approximately nine months Embryonic Development - Months 1-2 Formation of major organs Fetal Development - Months 3-9 Major organs become larger and refined

Human Embryonic and Fetal Development Biology, 9th ed, Sylvia Mader Chapter 44 Human Embryonic and Fetal Development Animal Development Embryonic Development First Week Morula transformed into blastocyst Blastocyst consists of A fluid-filled cavity A single layer of outer cells called the trophoblast gives rise to chorion Inner cell mass - develops into a fetus

Human Embryonic and Fetal Development Biology, 9th ed, Sylvia Mader Chapter 44 Human Embryonic and Fetal Development Animal Development Embryonic Development (continued) Second Week Implantation begins Trophoblast secretes human chorionic gonadotropin (HCG) Maintains corpus luteum, therefore maintaining the endometrium and preventing menstruation Hormone that is the basis of the pregnancy test Gastrulation occurs Inner cell mass flattened into embryonic disk Ectoderm, mesoderm, and endoderm differentiate

Human Embryonic Development Biology, 9th ed, Sylvia Mader Chapter 44 Human Embryonic Development Animal Development Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. amniotic cavity embryonic disk yolk sac blastocyst cavity trophoblast a. 14 days amniotic cavity embryo yolk sac chorionic villi chorion b. 18 days body stalk amniotic cavity embryo allantois yolk sac chorionic villi c. 21 days chorion amniotic cavity amnion allantois yolk sac chorionic villi d. 25 days chorion amniotic cavity digestive tract chorionic villi amnion umbilical cord e. 35+ days

Human Embryonic and Fetal Development Biology, 9th ed, Sylvia Mader Chapter 44 Human Embryonic and Fetal Development Animal Development Embryonic Development (continued) 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 Discernable eyes, ears, and nose

Human Embryo at Beginning of Fifth Week Biology, 9th ed, Sylvia Mader Chapter 44 Animal Development Human Embryo at Beginning of Fifth Week Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. brain tail brain optic vesicle optic vesicle pharyngeal pouch tail pharyngeal pouch heart region of heart, liver liver limb bud limb bud umbilical vessel umbilical vessel somite gastrointestinal tract limb bud a. b. a: © Lennart Nilsson, A Child is Born, Dell Publishing

Human Embryonic and Fetal Development Biology, 9th ed, Sylvia Mader Chapter 44 Human Embryonic and Fetal Development Animal Development Embryonic Development (continued) Sixth Through Eighth Weeks Head achieves normal relationship with the body as a neck region develops Nervous system is developed enough to permit reflex actions

Human Embryonic and Fetal Development Biology, 9th ed, Sylvia Mader Chapter 44 Human Embryonic and Fetal Development Animal Development The Structure and Function of the Placenta Placenta a mammalian structure that functions in gas, nutrient, and waste exchange between embryonic and maternal cardiovascular systems. Begins formation once the embryo is fully planted

Human Embryonic and Fetal Development Biology, 9th ed, Sylvia Mader Chapter 44 Human Embryonic and Fetal Development Animal Development The Structure and Function of the Placenta (cont.) Chorionic villi Project into the maternal tissues Surrounded by maternal blood sinuses The maternal and fetal blood do not mix Exchange between the fetal and maternal blood takes place across the walls of the chorionic villi CO2 and wastes move across from the fetus O2 and nutrients flow from the maternal side By the tenth week, the placenta is fully formed

Anatomy of the Placenta in a Fetus at Six to Seven Months Biology, 9th ed, Sylvia Mader Chapter 44 Anatomy of the Placenta in a Fetus at Six to Seven Months Animal Development Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. amniotic fluid placenta umbilical cord endometrium vagina umbilical cord umbilical blood vessel chorionic villi maternal blood vessels Placenta

Human Embryonic and Fetal Development Biology, 9th ed, Sylvia Mader Chapter 44 Human Embryonic and Fetal Development Animal Development Fetal Development and Birth Fetal development (months 3–9) involves: Extreme increase in size The genitalia appear in the third month A fetus soon acquires hair, eyebrows, eyelashes, and nails A fetus at first only flexes its limbs and nods its head Later it moves its limbs vigorously A mother feels movements from the fourth month on After 16 weeks, a fetal heartbeat is heard through a stethoscope. A fetus born at 24 weeks may survive

Preventing and Testing for Birth Defects Biology, 9th ed, Sylvia Mader Chapter 44 Preventing and Testing for Birth Defects Animal Development It is believed that at least 1 in 16 newborns has a birth defect Hereditary defects can sometimes be detected before birth Amniocentesis allows the fetus to be tested for abnormalities of development; Chorionic villi sampling allows the embryo to be tested; During preimplantation genetic diagnosis, eggs are screened prior to in vitro fertilization