Word Roots :

1. Word Roots: • arch- = ancient, beginning (archenteron: the endoderm-lined cavity, formed during the gastrulation process, that develops into the digestive tract of an animal) • blast- = bud, sprout; -pore = a passage (blastopore: the opening of the archenteron in the gastrula that develops into the mouth in protostomes and the anus in deuterostomes) • blasto- = produce; -cyst = sac, bladder (blastocyst: a hollow ball of cells produced one week after fertilization in humans) • contra- = against (contraception: the prevention of pregnancy) • -ectomy = cut out (vasectomy: the cutting of each vas deferens to prevent sperm from entering the urethra) • endo- = inside (endometrium: the inner lining of the uterus, which is richly supplied with blood vessels) • epi- = above, over (epididymis: a coiled tubule located adjacent to the testes where sperm are stored)

2. extra- = beyond (extraembryonic membrane: four membranes that support the developing embryo in reptiles, birds, and mammals) • fertil- = fruitful (fertilization: the union of haploid gametes to produce a diploid zygote) • gastro- = stomach, belly (gastrulation: the formation of a gastrula from a blastula) • labi- = lip; major- = larger (labia majora: a pair of thick, fatty ridges that enclose and protect the labia minora and vestibule) • oo- = egg; -genesis = producing (oogenesis: the process in the ovary that results in the production of female gametes) • soma- = a body (somites: paired blocks of mesoderm just lateral to the notochord of a vertebrate embryo) • tri- = three (trimester: a three-month period) • tropho- = nourish (trophoblast: the outer epithelium of the blastocyst, which forms the fetal part of the placenta)

3. Development Characteristics of Animals

4. Asexual Reproduction Creation of offspring whose genes all come from one parent without the fusion of egg and sperm

5. Budding • Splitting off new individuals from existing ones • Yeast cells, hydra

6. Binary Fission • 1  2 of ~ equal size, w/identical genetic info of the parent • Prokaryotes, algae, bacteria

7. Fragmentation • Breaking of parent body into several pieces • Must be accompanied by regeneration (regrowth of body parts from pieces) • Can occur if pieces develop into clones or if part of body grows back

8. Parthenogenesis • Egg develops in absence of fertilization by sperm through mitotic cell division • Occurs naturally in bees to form male drones • Artificially in some animals (rabbits, frogs)

9. Regeneration • Ability of certain animals to regrow a missing body part • Sometimes parts of animal grow into complete animal (planaria, earthworm, lobster, sea star) • Similar to vegetative propagation in plants

10. Advantages of asexual reproduction • Isolated organisms can reproduce • Produce many offspring quickly with no time or energy lost in gamete production or fertilization • Quick expansion of population of animals genetically well suited for particular environment

11. Disadvantage of asexual reproduction • Produces genetically uniform population • If the environment changes and becomes less favorable to survival, all individuals may be affected equally, and entire population may die out

12. Sexual Reproduction Creation of offspring by fusion of two haploid (n) sex cells (gametes) to form a diploid (2n) zygote

13. Advantage of sexual reproduction • Increases genetic variability among offspring from meiosis and random fertilization • Provides greater adaptability to changing environments • More costly in energy than asexual • Increases diversity in population by creating new combinations of alleles in offspring

14. Fertilization • Union of sperm and egg to form diploid zygote • Activates egg by triggering metabolic changes that start embryonic development

15. 3a. Proteins on sperm head bind to receptor protein molecule 4a. Species-specific protein molecules on surface binds with specific receptor proteins on vitelline layer-ensures that sperm of other species cannot fertilize egg 5a. Fertilization membrane forms

16. Fertilization envelope • No other sperm can enter once membranes fuse because plasma membrane becomes impenetrable to other sperm cells • Vitelline layer hardens and separates from plasma membrane • Space becomes filled with water and vitelline layer becomes fertilization envelope, another barrier impenetrable to sperm

17. Embryonic development • Mitotic cell divisions of zygote and early embryo-cleavage divisions: • Rapid mitotic cell division of zygote • 1-celled embryo (zygote)  multicellular embryo • 1st cells (blastomere) result from divisions of a fertilized egg cell • No cell growth, only division of cytoplasm • Size decreases with cell divisions from 2-, to 4- to 8- cell

19. Morula • Solid ball of 16-32 cells • Cells are compacted • Individual blastomeres become progressively smaller but size of embryo remains same (still no embryo growth)

20. Morula EarlyBastula LateBastula

21. Blastula • Spherical structure produced by cleavage of a zygote • Outer single layer of cells (blastoderm) surround fluid-filled cavity (blastocoele) • First time two cell types are present-differentiation starts • First stage where embryo grows in size

22. Gastrulation • As embryo continues to grow, some cells of blastula fold inward, forming 2-layered gastrula • Outer surface-ectoderm • Eventually form skin, eyes, nervous tissue • Inner surface-endoderm • Develop into viscera, including lining of digestive tract, respiratory system, lungs

23. EarlyGastrula Gastrula EarlyGastrula

24. Opening of indented space (opening of primitive digestive tract in an embryo): Protostomes-develops into mouth in Nematodes, Annelids, Insecta, Crustaceans Deuterostomes-develops into anus in Echinoderms, Hemichordates, Chordates

25. Development continues until mesoderm formed 3rd cell layer to form between other 2 forms circulatory, reproductive, and digestive systems, endocrine glands, muscles, blood, and bone

29. Animals groups distinguished by # germ layers (embryonic tissue layers) • One layer-Porifera • Diploblastic- • Two tissue layers-endoderm, ectoderm • Some (Cnidarians) • Triploblastic- • Three tissue layers-endoderm, ectoderm, mesoderm • Others (both protostomes/deuterostomes)

31. Symmetryrepetition of parts in animal or plant in orderly fashion • Correspondence of body parts, in size, shape, and relative position, on opposite sides of dividing line or distributed around central point or axis • Asymmetrical animals-most sponges • No general body plan or point of symmetry that divides body into mirror-image halves • Radially symmetrical animals-anemones and sea stars • Body parts organized around central point and tend to be cylindrical in shape • Can be cut along any number of lines to get halves that are roughly mirror image • Bilaterally symmetrical animals-humans and fish • Body parts arranged the same way on both sides • Can only use 1 line to get halves that are roughly mirror images

33. Animals are divided by types of body cavity and its development: • Acoelomates-platyhelminthes • Lack enclosed body cavity • Endoderm, mesoderm, and ectoderm

34. Pseudocoelomates-nematodes • Fluid-filled central cavity that lies between gut and mesodermal tissue layers (pseudocoelom) • Cavity not been considered true coelom, because • True mesenteries not present-partially lined • Development in embryo is quite different • Move more efficiently-acts like watery skeleton against which muscles can work

35. True coelomates-most animals • Fluid-filled body central cavity-coelom • Internal space that surround digestive tract or other internal structures • Exists within mesoderm • Gut suspended within it by sheets of tissue-mesenteries • Gives animal flexibility, protects organs from external blows, provides space for expansion of organs, like stomach

38. Summary of Evolutionary Trends *Although echinoderm adults are radial, they are grouped with bilateral animals because their larvae are bilaterally symmetrical and they evolved from bilaterally symmetrical ancestors