Developing Zygote Seeds, Eggs, Embryos

Developing Zygote Once sperm and egg have fused to form a zygote, the zygote divides and becomes an embryo. The embryo develops into the organism. Embryos are protected when they develop inside seeds, eggs, or the mother.

Seeds A seed is a fertilized ripened ovule of a flowering plant. Basic parts of a seed: embryo, stored nutrients, seed coat (protection)

Stored Nutrients The nutrients supply energy for the embryo to develop until it can produce its own food by photosynthesis. The nutrients are in the form of either sugar or starch Most of the world’s food comes from seeds of three plants: corn, rice, wheat.

Embryo – precursor to seedling plant The embryo is the “baby plant” in the seed consisting of precursor tissues the will become the seedling: Cotyledon  first leaves Radical  Roots Epicotyl  Stem and Leaves Hypocotyl  stem below cotelydon Cotyledons get smaller as the embryo grow and food is used up. Once first leaves develop, the cotyledons drop off. In monocots, cotyledon is important in food absorption, whereas endosperm serves as a food storage tissue. Usually, in mature seeds of dicots, cotyledon is present while endosperm is absent. 

Two types of seeds Seeds contain seed leaves called cotyledons There are two types of seeds: Monocotyledons produce one seed leaf. Eg. corn Dicotyledons produce two cotyledons. Eg. beans

Two types of seeds When seeds germinate (start to grow), they will use the food in the cotyledons. In corn, food is supplied by the endosperm.

Anatomy of a seed

EGGS

protection (shell, jelly-like substance, or egg case). Eggs contain: Zygote/embryo, some nutrients, protection (shell, jelly-like substance, or egg case). An egg case may contain many eggs eg. Tape worm egg case

Amniotic Eggs contain a single embryo surrounded by a shell. Eg birds and reptiles

Yolk sac – stored nutrients Amnion- a fluid-filled sac, cushions the embryo Allantois holds waste produced by the embryo Chorion (along with allantois) controls the movement of gases and wastes in and out of egg. Albumen also cushions embryo and supplies additional nutrients Chorion – outermost membrane

How do animals protect their eggs/developing embryos? bury their eggs (sea turtles) Incubate them in a nest (birds) Incubate them inside their bodies (all mammals except monotremes)

Monotremes Mammals that lay eggs. duck billed platypus, spiny anteaters https://www.youtube.com/watch?v=Ot-CUOidbFk meaning "one hole“ - named so because of the presence of single cloacal opening in their bodies that serves as a passage for eggs or sperms, feces and urine. but nurse their young with milk

Embryos that Develop in the Mother Placental Mammals and Marsupials

Embryos that develop in the Mother Embryos of all mammals except duckbill platypus and spiny anteaters, develop inside the mother. Embryos of marsupials must crawl from birth canal to nipple in a pouch.

Marsupials Embryos of Marsupials are only partially developed when born and finish developing in their mother’s pouch. Eg. kangaroos, koalas, and opossums https://www.youtube.com/watch?v=2lCKc8tURtc Embryos of marsupials must crawl from birth canal to nipple in a pouch.

Marsupilas

Placental Mammals Embryo develops longer inside, where a placenta connects the fetus to the mother. Eg. Humans, dogs, whales. Monotremes exception – they are mammals that lay eggs

Placental Mammals The fetus is attached to the placenta via an umbilical cord, which carries wastes out of fetus and nutrients in. Three different ways animals give birth: https://www.youtube.com/watch?v=sz 3Yv3On4lE Embryos of marsupials must crawl from birth canal to nipple in a pouch.

Sex Determination – more complicated than you thought Ted Ed video https://ed.ted.com/lessons/sex-determination-more- complicated-than-you-thought HW: Zygote WS

Label the parts of the seeds

Reproductive Technologies in Agriculture 3.5 VOCABULARY selective breeding artificial insemination in vitro fertilization recombinant DNA technology genetically modified organisms (GMOs) Selective breeding is used to produce desirable traits in plants and animals. Vegetative reproduction techniques are used to produce more plants faster. Artificial insemination and in vitro fertilization are used in the breeding of many domestic animals. Fish hatcheries increase the number of fertilized eggs. Recombinant DNA technology is used to produce some drugs for humans. Some genetically modified organisms (GMOs) may have desirable traits, but since they contain DNA from other organisms, their existence raises moral and ethical concerns.

Monocotyledons Eg. corn

Monocotyledons