Life Cycles, Reproduction

and Heredity

Reid Pierce

Fulbright Jr. High

Bentonville, AR

Reproduction

Bottom Line: An organism must

reproduce in order for that species to

continue.

How do they reproduce?

…I’m glad you asked

Reproduction

All living things are made of cells.

Cells divide in order to grow, replace

worn out/dead cells and reproduce

Inside each nucleus are chromosomes

(DNA)

DNA determines an organisms traits

(such as hair color, blood type, etc…),

and controls cell processes

Chromosomes

Organized structures of

DNA

The number of

chromosomes can vary

greatly between species.

Each organism gets half

of its chromosomes from

the male and half from

the female

Male sperm

carry 16

Female egg

cells carries 16

Alligators have 32 chromosomes

• 11 from the pistil (female) and 11 from

the stamen (male)

• 29 chromosomes from the

male and 29 from the

female

Beans have 22

Channel Catfish have 58!

Evening Primrose has 28

Violets have 50

White Campion have 22

King Crab have 208!

Porpoise have 44

But Shrimp have 254!!!

Mosquitoes only have 6!

How can they have the

same number of

chromosomes?!

Different genes located on

the chromosomes

Tiger Lily have 24

Tomatoes have

24

And humans have… 46

Does half yellow and half blue

make green?

Gregor Mendel, 1860:

Traits do not blend. Traits are shuffled.

Cell Division

Two types of cell division:

1. Mitosis - produces new body cells in order to

grow and replace worn out / damaged cells Skin cells, Muscle cells, Heart cells, etc…

Mitosis

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

Cell Division

Two types of cell division:

1. Mitosis - produces new body cells in order to

grow and replace worn out / damaged cells Skin cells, Muscle cells, Heart cells, etc…

2. Meiosis - produces new reproductive cells in

order for the organism to reproduce Sperm Cells, Egg cells

Meiosis

Reproduction

Two types of reproduction:

1. Asexual Reproduction – a type of reproduction

in which a genetically identical organism is

produced from one parent (Ex. body cells dividing

or potato buds forming)

Asexual Reproduction

In Plants

Extremely common in plants Vegetative Reproduction – tulip bulbs dividing

Budding – potatoes, yeast

Runners – strawberries

Potato bud will make a

new Potato plant.

Asexual Reproduction

In Animals

The primary form of reproduction in single cell

organisms (such as bacteria and

paramecium).

Binary Fission

Paramecium dividing

into two paramecium

Asexual Reproduction

In Animals

Other methods: Fragmentation – worms, starfish, etc… (some plants -

lichens)

Parthenogenesis – unfertilized egg develops

Asexual Reproduction

Advantages:

Very rapid population growth (everyone can

reproduce, don’t waste time finding a mate, etc…)

Requires less energy

Only one parent needed to continue or start a

colony of the species (an island)

Disadvantages:

Limits genetic diversity (species doesn’t change)

Reproduction

Two types of reproduction:

1. Asexual Reproduction – a type of reproduction

in which a genetically identical organism is

produced from one parent (Ex. body cells dividing

or potato buds forming)

2. Sexual Reproduction – the joining of a male

sperm cell and a female egg cell creating an

organism genetically different from the

parents

Sexual Reproduction

In Plants

Flowers!

Sperm cell is pollen that is produced by

and located on the anther (the male part of

the flower)

Egg is produced by and located

in the ovary (the female part of the flower)

Sexual Reproduction

In Animals

• Sperm cells: • the male reproductive cell

• has a head and a tail

• carries genetic information from the father

• Egg cells: • the female reproductive cell

• site of fertilization

• carries genetic information from the mother

Sexual Reproduction

Advantages:

Promotes genetic diversity (species can change

and adapt to their environment)

Disadvantages:

Slower population growth

Requires more energy

Male & female are needed to continue or start a

colony of the species

Asexual or Sexual?

Tulip bulbs dividing

Flowers being pollinated

Strawberries producing runners

Sperm cell fertilizing egg cell

How many chromosomes

do humans have? 46

-When the 23

chromosomes from the

female (contained in the egg)

join the 23 chromosomes

from male (contained in the

sperm) it is called a

zygote.

Vertebrate Development

In vertebrates there are 3 stages

of vertebrate development:

1. Zygote

2. Embryo

3. Fetus

Vertebrate Development

1st stage: Zygote – a fertilized egg.

Vertebrate Development

Once the egg has been fertilized (zygote) it has genetic information from the mother and father and it begins to divide to produce a multicellular organism.

Vertebrate Development

The result of the zygote dividing by mitosis is the 2nd stage – an embryo – a fertilized egg that has begun to divide – less than 4 days after fertilization.

Vertebrate Development

At about 9

weeks it enters

the 3rd stage

and is called a

fetus – major

structures have

formed – 9

weeks to birth.

Human fetus at 9 weeks