Unit 3 – Evolution, Heredity and Genetics

Read the “Cells that Reproduce” article and answer the questions with a partner.

What questions will I be able to answer by the end?

• How do I inherit my traits?• What is the probability that my children will have

curly or straight hair?• How does my body repair itself when I break a bone

or get a cut?• How have ducks acquired webbed feet over time?• Why are polar bears white?• I have freckles but my sister doesn’t. How does this

happen?

Asexual vs. Sexual Reproduction

•Reproduction is the ability for an organism to make more of its kind.

• Cells come from other living cells.• Cells reproduce (make more cells) by

dividing into two.• This is called mitosis, and it is a form

of asexual reproduction.

Asexual reproduction- one parent organism produces

two or more offspring that have the same genetic material as the parent.• Low variation of offspringEx: Cell splits into two -->

Offspring – the “child” of a parent organism

How do organisms reproduce asexually?

Small, unicellular organisms undergo asexual reproduction through cell division (mitosis) and budding.

Asexual reproduction: Cell division

This is an example of a bacteria undergoing cell division.

How many parents?How many offspring?

Asexual reproduction – Cell division

This is a paramecium undergoing cell

division. How many parents?

How many offspring?

We have cell division going on in our bodies too:

Our body cells go through cell division for growth and repair:• One bone cell divides to make 2

new bone cells (we grow taller over time!)• One skin cell divides to make 2 new

skin cells (we repair a cut in our skin)

How else do organisms reproduce asexually?

Asexual Reproduction: Budding

This is a hydra. A new organism is

forming on its side and can live on its

own once it falls off.How many parents?

How many offspring?

If small organisms and cells undergo asexual reproduction, how do larger, more complex

organisms like humans reproduce?

Sexual reproduction• Occurs in larger, complex organisms• Step 1: Meiosis creates gametes • Step 2: Gametes unite to form offspring (fertilization)• Gametes:– Sperm cell (male)– Egg cell (female)

• Involves 2 parents and one or many offspring.• Produces high variationEx: human sperm fertilizes a human egg during sexual

intercourse and a new organism is formed.

homework• Cut out the images given to you.• determine which side of the chart they belong

on – asexual reproduction or sexual reproduction.

• Fill in the blanks and answer the questions on the worksheet entitled Asexual vs. Sexual Reproduction Practice.