SEXUAL REPRODUCTION IN HIGHER ORGANISMS Handout # 21

1. Protozoans – (animal Like Protists) Paramecia – reproduce sexually by __________. This is the process by which ____________ _____________________. Diagram:Conjugation Two paramecia exchange heredity material

2. Hermaphrodites – Examples: - contain functional gonads of both sexes. - can produce egg cells & sperm cells EarthwormsHydra

3. Sperm Cells – a.size – ________________________________ b.shape – ______________________________ _______________________ c. locomotion – ___________________ __________________________ d. number – ____________________________ Microscopic – no yolk (smaller than egg cell) Pollywog shape – Head of cytoplasm and Chromosomes and a flagellum. Moves by lashing its tail – Needs moisture to survive and move Millions (many) *remember 1  4 meiosis

Diagram: Sperm cell

4. Egg Cells – a.size – ______________________ _______________ Largest to > Smallest BirdsReptiles Amphibians Fish Mammals b. shape – ______________________________ __________________________ c. locomotion– __________________________ __________________________ Much larger than sperm cells. Some are very large Round nucleus in center w/large amount of cytoplasm & yolk surrounding it No means of movement. Moved in Female oviduct by tiny cilia (hairs)

Egg Cells – cont. d. number – ____________________________ __________________ Very small in comparison to the number of sperm cells produced

5. Fertilization – restores the _______ number of chromosomes. (2__) A ______ is formed. a. external fertilization– union of egg and sperm __________ female’s body. -usually a water environment – Why? ____________________________diploid n zygote outside the Sperm need to swim to the egg.

External fertilization– cont. This also involves large numbers of eggs and sperm produced. There is little or now parental care. Why? ___________________ _________________________________ ___________ - It is outside the body -It increases the chance for fertilization -And survival

b. internal fertilization – union of egg and sperm ______ the female’s body. This is characteristic of land-dwelling animals. Why? ________________________ Few eggs are produced at one time. Why? _______________________________ _______________________________ _________ inside No water for sperm to swim. They are protected and have a better chance of fertilization & survival.

6. Development – a. External Development – occurs _______ female’s body. The embryo obtains food from the yolk in the egg. Parents provide little or no care for their young. examples: ______, ________________________, a few _________, ___________________________ ____________________ outside Fish Birds, Reptiles & Amphibians Mammals (Monotremes) – Spiny Anteaters & Duck-billed Platypus

Yolk Sac Diagram of a Bird’s Egg Structure: Blood Vessels B B Amnion Allantois Shell Embryo Chorion C D E F G Yolk Sac A Label the diagram in your notes (clockwise) starting in the bottom left hand corner of the diagram as structure A.

Function: Use this diagram to complete your notes with the functions of the labeled structures Most of the CO 2 produced by the chicken embryo is released through the shell.

b. Internal development– occurs ______ the female’s body. Usually there is little or no yolk in the egg because the young is nourished by the mother. examples: most __________ Placental Mammals – __________ ____________________________ inside Mammals Egg cells in female – internal fertilization - form placenta – food and O 2

Placenta – ______________________________________ ______________________________________ _______ It is rich in ___________ and __________ blood vessels. The _________ ____ connects the embryo to the placenta. It contains blood vessels that carry materials between the mother and the embryo. In the placenta the exchange of materials is by _________ and _______ __________. **THE BLOOD OF THE MOTHER AND THE BABY NEVER MIX.** Temporary organ between mother & embryo, made of maternal and embryonic tissues embryonicmaternal umbilical cord diffusio n active transport

Diagram – The mammalian embryoPlacenta Oviduct Uterus Umbilical Cord Embryo Amnion

Marsupials – _______ mammals. examples - They have _______, fertilization, and the embryo obtains nourishment from the yolk for a short time. They are born NOT fully developed. After birth, they crawl to a mammary gland and remain there until development is complete.Pouched Kangaroo, Koala Bear, Opossums internal

Parental Care The greatest parental care is associated with organisms that carry on _______ fertilization and _______ development. Animals that produce on or two eggs during their reproductive cycle have ________ fertilization and ________ development. internal internal interna l internal

Advantage of Internal Fertilization One advantage of internal fertilization over external fertilization is that the zygote survival is increased. The number of egg cells produced by an organism is dependant upon the organisms 1. __________________________ 2. __________________________ 3. __________________________ **REPRODUCTIVE EFFICIENCY IS GRETEST WITH __________ FERTILIZATION AND __________ DEVELOPMENT. Method of fertilization Type of development Parental care given to young INTERNAL INTERNAL

Fertilization Diagram:

Another View

Stages of Development: The early stages of embryonic development are similar in all animals.

1. Zygote - A fertilized egg ZYGOTE

2. Cleavage - Series of rapid cell divisions in a zygote  embryo ZYGOTE CLEAVAGE ZYGOTE AFTER EIGHT DIVISIONS

3. Morula - The solid ball stage (of cells) ZYGOTE AFTER EIGHT DIVISIONS CLEAVAGE MORULA

4. Blastula - The hollow ball stage (of cells) MORULABLASTULA CLEAVAGE

5. Gastrula - gastrulation - BLASTULA CLEAVAGE GASTRULA The cup shaped stage (of cells) Formation of the gastrula

** note that during cleavage the size of the developing embryo does not increase but the number of cells do. How is this possible?

mesoderm endoderm ectoderm The Germ Layers

The Three Germ Layers Three Germ Layers form (eventually) _________, _________, __________. After gastrulating, the embryo goes through differentiation (specialization)ectoderm endodermmesoderm

6. Differentiation - each layer gives rise to specific body parts. A. ectoderm – Nervous System, Skin B. endoderm – Lining of Digestive and Respiratory Tracts, Liver, Pancreas C. mesoderm – Muscles, Skeleton, Circulation system (Blood), Excretory system, Reproductive system C B A

Summery Cell Layers  Tissues  Organs  Organ systems  Organism (Really the last stage is of development DIFFERENTIATION and GROWTH.) Growth now involves both an increase in size and number of cells.