Transcript Reproduction

Unit 4 – Lecture 1
Reproduction
 Reproduction – producing offspring
by sexual or asexual means
 Two types:
 Asexual Reproduction
 Sexual Reproduction
Asexual Reproduction
 Asexual Reproduction
 single “parent” cell produces genetically
identical offspring on it’s own
 mostly prokaryotes
Asexual Reproduction – cont’d
 Five Types:
 binary fission – cell splits into two identical cells

used by single celled organisms; mostly
prokaryotes
Asexual Reproduction – cont’d
 [Five Types:]
 fragmentation – parts of organism can grow into
complete new organism
 planaria, sponges, starfish, many plants
Asexual Reproduction – cont’d
 [Five Types:]
 budding – new cells grow off of original cell and
break off [yeast]
Asexual Reproduction – cont’d
 [Five Types:]
 vegetative reproduction – new plants grow from a
part of the living plant that is still connected.
[dandelions, potatoes…etc]
Asexual Reproduction – cont’d
 [Five Types:]
 parthenogenesis – rare occurrence; egg does not
need to be fertilized to produce offspring
 water fleas, bush cricket, dandelion, even types of
reptiles and possibly certain sharks
Asexual Reproduction – cont’d
 Advantages:
 very quick
 does not depend on multiple of same
organism being present
 Disadvantages:
 genetic problems all passed to offspring
 no biodiversity

if environment changes and all organisms have
same genes…they may not be well-suited to the
environment anymore.
Discuss
 With what you just learned about asexual
reproduction, what do you think are the advantages
and disadvantages of sexual reproduction?
Sexual Reproduction
 Sexual Reproduction
 two parent organisms donate genetic information to
form offspring
 genetic information is held in the gametes
 gamete = sex cell [egg, sperm];
formed by meiosis
 fertilization = gamete + gamete = zygote
 zygote grows into fetus
Sexual Reproduction – cont’d
 Advantages:
 genetic diversity

more likely to survive in changing environments
 Disadvantages:
 must have more than one organism
 takes more time and energy



find mate
produce gametes
go through meiosis to form gametes
Chromosomes
 Organisms have their own number of chromosomes –
specific to their species
 “ploid” or “ploidy” = refers to chromosomal number
Chromosomes – cont’d
 Sexual reproduction leads to diploid organisms
 diploid – contain two sets of chromosomes
humans = 23 pairs = 46 total chromosomes
 called “2n” [n = # of chromosome sets]
 normal, somatic cells are diploid
 “soma” = body
 haploid – contains only one set of chromosomes
 diploid organisms have haploid gametes
[sex cells; egg & sperm]
 called “1n”

Chromosomes – cont’d
 Homologous Chromosomes
 chromosomes with the same information in the
same locations
 we have 2 sets of homologous chromosomes
 1 set from each parent
Chromosomes – cont’d
 [Homologous Chromosomes]
 karyotype – organized
profile of a person’s
chromosomes
Chromosomes – cont’d
 [Homologous Chromosomes]
 22 pairs are autosomes
autosome = non-sex determining chromosome
 same location on chr = same gene
 gene = area of a chromosome [or in DNA]
which codes for a certain trait
 1 pair are sex chromosomes [X or Y]
 two X [XX] = female
 one X & one Y [XY] = male

Homework:
 Using your book and your knowledge of Mitosis…
 notes: similarities and differences between meiosis
and mitosis [ch 10 whale; ch 11 cheetah]
 finish ½ of worksheet by tomorrow [while you take
the notes]
 we will discuss it tomorrow.