REPRODUCTION • Species need to reproduce in order to survive • Not all individuals of that species may reproduce-remember, evolution said that only the “fittest” survive to pass on those “fit” genes
Two kinds of reproduction- • Remember?…… • ASEXUAL reproduction: one parent, offspring is genetically identical to parent • Examples are binaryfission in unicellular organisms, runners in spider plants
Faster than sexual reproduction, and no other organism is necessary No variation…..if organism is perfectly adapted for that environment, exact copies will also be perfectly adapted No variation is also the DISADVANTAGE- if the environment changes, there may be no chance of the species surviving in that new environment-what if the peppered moth had only one version? Advantages of asexual reproduction
Cell division- • In Asexual Reproduction is MITOSIS (or a similar process)- • Makes exact copies-CLONES- (except now we know about mutations)
And SEXUAL Reproduction • TWO parents, offspring is genetically different from either parent • Adds variation to a species
GAMETES • Are produced after MEIOSIS • Gametes fuse during FERTILIZATION • Fertilized egg-ZYGOTE-undergoes rapid mitosis and differentiation to become- • An EMBRYO
CONJUGATION • Occurs in Protists and some algae • Two organisms exchange genetic material to create a new variation, although they don’t create another organism until they undergo binary fission.
‘Member Plant Reproduction? • Flowers Are the reproductive organ of anthophytes (angiosperms) • Cones are the reproductive organs of gymnosperms • Other plants also use sperm and egg in a different strategy
But, let’s get to the animals- • GAMETES (AKA…..germ cells)–sperm and egg (ovum)- are produced in the gonads-testes and ovaries • Some organisms-worms and snails-have both testes and ovaries, but they exchange sperm packets
Can be INTERNAL, where sperm and egg meet inside the body of the female Occurs in land animals-insects, turtles, humans Can be EXTERNAL, where the sperm and egg meet outside the body of the female Usually occurs in animals that live in water (Remember: those sperm HAVE TO swim)-fish, frogs FERTILIZATION
MATING BEHAVIORS/Pollination Strategies • Insure that the organism is the same species (fish look the same even to fish) • Insures that the egg will be fertilized at the correct time • Insures only the “fittest” reproduce
Can be INTERNAL- inside the body of the female, partially (marsupials) and fully (placental mammals) Can be EXTERNAL-outside the body of the female, in eggs with no shells (fish), soft shells (turtles), hard shells (birds) DEVELOPMENT
And then, there’s the weird ones---- • Insects and frogs undergo metamorphosis, where development is finished after hatching • Some snakes and sharks hold their eggs inside and give birth to live young • And the seahorses….!!!!
Development refers to- • The process from fertilized egg to living outside of egg or Mom • But, really, development happens for the organism’s entire lifetime
DIFFERENTIATION (that other “D word) • Happens soon after fertilization • Cells change in structure to prepare for different functions • Some genes “turn on” and others “turn off” • Organisms that can regenerate have cells that return to the embryonic state
The PURPOSE of reproduction • Is to create a new organism of the same species that will survive, whatever the strategy.
HUMAN Animals • Have INTERNAL FERTILZATION • Fully INTERNAL DEVELOPMENT, where the placenta and umbilical cord maintain the embryo inside the uterus
After Nine Months GESTATION • The placenta is no longer efficient enough to maintain the fetus, so it’s time for her or him to get out of there !
DEVELOPMENT • Continues for a long time in humans, most dramatically in the first years • Human children have an extended time of parental care • Aging happens from birth till death
HORMONES • Direct the changes that occur during development and growth • Begin maturing of egg and production of sperm at PUBERTY, usually in the early teens.
The Ability to Reproduce- • Wanes as humans age • Females cease menstruation at MENOPAUSE, after age 50 • Males continue to produce sperm throughout lifetime