REPRODUCTION Species need to reproduce in order to survive Not all individuals of that species may...

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 binary fission in unicellular organisms, runners in spider plants

Advantages of asexual reproduction

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?

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

FERTILIZATION

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

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

DEVELOPMENT

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)

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

Next- Human Reproductive Systems