Unit IV:
Can You Divide?
Cell Reproduction
• All organisms REPRODUCE.
• Why?
– This allows for growth, development and
the survival of the species
There are 2 types of
reproduction
1. Asexual Reproduction
– Requires A single parent!!! (sorry, just
ONE).
Asexual Reproduction (cont)…
• Results in the offspring having the same
hereditary material (DNA)
Asexual Reproduction (cont)…
• In other words, the new cells are an exact
copy of its parent (allow for little variation
among species)
Types of Asexual Reproduction
• Fission – cell splits in half (ex: Amoeba)
Types of Asexual Reproduction (cont)…
•
Budding – a new organism grows off
from the side of an adult (ex: Hydra)
Types of Asexual Reproduction (cont)…
• Regeneration – a new organism grows
from a severed body part (ex: starfish)
What is a chromosome?
• Structure found in the nucleus of a
eukaryotic cell that contains hereditary
material
The structure of a chromosome
Chromatid arm
Centromere
Chromosome
Gene
How do we replace old skin cells?
• Mitosis
– The process in which the newly duplicated
chromosome pairs are separated from each
other
What happens to a cell before
Mitosis starts?
• Interphase
– Cell grows and develops
– Chromosomes duplicate themselves
– Centrioles appear
Steps of Mitosis
• Prophase
– Nuclear membrane disappears
– Centrioles move to opposite ends of the cell
– Spindle fibers appear in the cell
Steps of Mitosis Continued
• Metaphase
– Chromosomes line up in the center of the cell
– Centromeres attach to the spindle fibers
Steps of Mitosis Continued
• Anaphase
– Centromeres separate
– The two strands of chromosomes are pulled
apart by centrioles towards opposite ends of
the cell
Steps of Mitosis Continued
• Telophase
– Centrioles and spindle fibers disappear
– Nuclear membrane begins to reappear
What happens to a cell after Mitosis
is complete?
• Cytokinesis
– Cell splits into two identical daughter cells
with complete set of organelles
How did you get here?
• Sexual Reproduction
– Reproduction in which two (2) parents are
involved
– Sex cells are called gametes (egg and
sperm cells are gametes)
What is sexual reproduction?
• Sexual reproduction
– starts with the formation of gametes and
ends when one gamete joins another gamete.
The joining of egg and sperm is called
fertilization, resulting in the production of a
zygote
zygote
How are gametes produced?
• Meiosis
– A process whose purpose is to reduce the
chromosome number in the cells
– Produces 4 new cells with half the number of
chromosomes as the parent
Meiosis – two divisions of the nucleus
Parent Cell
1st Division
2nd Division –
4 new daughter
cells with ½ the #
of chromosomes
Meiosis continued
• Diploid Cells: have two of every
chromosome (body cells)
• Haploid Cells: have just one
chromosome from each pair (gametes)