Textbook Notes (378,431)
CA (167,129)
UTSC (19,207)
BIOA02H3 (153)
Chapter 42

Chapter 42 Textbook notes

7 Pages
71 Views

Department
Biological Sciences
Course Code
BIOA02H3
Professor
Andrew Mason

This preview shows pages 1-2. Sign up to view the full 7 pages of the document.
Ch 42 REPRODUCTION
42.1
How do animals reproduce without sex?
x Sexual reproduction is universal in almost all organisms
x Some can reproduce sexually and asexually and some can only reproduce
asexually
x Offspring that are reproduced asexually are identical to each other and parents
o Can convert resources to reproduce
o 'RQWKDYHWRORRNIRUDPDWH
o But does not have the genetic diversity that comes with sexual
reproduction which is a disadvantage in changing environments
x Animals that reproduce asexually are usually invertebrates
o Are sessile
o &DQWORRNIRUPDWHV
o 'RQWKDYHPDWHVDURXQG
o Live in constant environment where reproducing asexually would be
advantageous
x Three ways animals reproduce asexually is by
1. budding,
2. regeneration
3. parthenogenesis
Budding and regeneration produce new individuals by mitosis
x Budding²new individuals form as outgrowths or buds from older animals
o Bud formed by mitosis
o Bud is identical to parent
o Can grow to be as big as parent before being independent
x Regeneration
o Usually thought as replacing damage tissue or lost limbs
o But some organisms can regenerate to a new individual
o If you cut a sea star into individual pieces then each piece will become an
individual organism
x Parthenogenesis
o The development of unfertilized eggs
o Occurs in arthropods and some fish, amphibians and reptiles
o Some species parthenogenesis determines sex²honey bees, males come
from unfertilized eggs, females come from fertilized eggs
www.notesolution.com
o Parthenogenesis sometimes requires sexual behaviour²like in whiptail
lizards,
All are female
Some will act like male to stimulate another female to release eggs
Whether they act like a male or female depends on hormonal
states²when estragon levels are high it acts female, when estragon
levels go down and progesterone levels go up, then it acts male
42.2 How Do Animals Reproduce Sexually
x Large portion of time and energy budgets of sexually reproducing animals goes
into mating
o Mating exposes them to predators and usually takes a lot of energy, also
keeps them from doing other things like feeding and taking care of
existing offspring.
x Sexual reproduction requires 2 haploid cells to come together to make a diploid
individual.
o Haploid cells are also called gametes
o Gametes are formed by gametogenesis
x Sexual reproduction has 3 parts
o Gametogenesis (making gametes)
o Mating (getting gametes together)
o Fertilization (fusing gametes together)
Gametogenesis produces eggs and sperm
x Gametogenesis happens in the gonads²testes in males and ovaries in females
x Gametes formed in males are sperm and eggs in female
x Sperm moving using a flagellum and eggs are non-motile
x Gametes form from germ cell²different from other cells in the body which are
somatic cells
x Germ cells are secluded in the body until gonads start to form
x Then germ cells go to the gonads and by mitosis become spermatagonia and
oogonia which are diploid
x They multiply by mitosis and become primary spermocytes and primary oocytes
x Then through meiosis the chromosomes reduce to haploids²these become sperm
and ova
Spermatogenesis
x Mitosis in embryo comes before male germ cells become spermatogonia
x Primary spermocytes divide by meiosis to form secondary spermocytes
x Secondary spermocytes become 4 haploid spermatids
x Spermatids are connected by cytoplasmic bridges
o Bridge happens because of asymmetry in sperm cells²one get X and the
other gets Y, X chromosomes have more genes than Y. some genes on the
www.notesolution.com

Loved by over 2.2 million students

Over 90% improved by at least one letter grade.

Leah — University of Toronto

OneClass has been such a huge help in my studies at UofT especially since I am a transfer student. OneClass is the study buddy I never had before and definitely gives me the extra push to get from a B to an A!

Leah — University of Toronto
Saarim — University of Michigan

Balancing social life With academics can be difficult, that is why I'm so glad that OneClass is out there where I can find the top notes for all of my classes. Now I can be the all-star student I want to be.

Saarim — University of Michigan
Jenna — University of Wisconsin

As a college student living on a college budget, I love how easy it is to earn gift cards just by submitting my notes.

Jenna — University of Wisconsin
Anne — University of California

OneClass has allowed me to catch up with my most difficult course! #lifesaver

Anne — University of California
Description
Ch 42 REPRODUCTION 42.1 How do animals reproduce without sex? N Sexual reproduction is universal in almost all organisms N Some can reproduce sexually and asexually and some can only reproduce asexually N Offspring that are reproduced asexually are identical to each other and parents o Can convert resources to reproduce o 439K,;094O44N147,2,90 o But does not have the genetic diversity that comes with sexual reproduction which is a disadvantage in changing environments N Animals that reproduce asexually are usually invertebrates o Are sessile o ,39O44N1472,908 o 439K,;02,908,74:3 o Live in constant environment where reproducing asexually would be advantageous N Three ways animals reproduce asexually is by 1. budding, 2. regeneration 3. parthenogenesis Budding and regeneration produce new individuals by mitosis N Buddingnew individuals form as outgrowths or buds from older animals o Bud formed by mitosis o Bud is identical to parent o Can grow to be as big as parent before being independent N Regeneration o Usually thought as replacing damage tissue or lost limbs o But some organisms can regenerate to a new individual o If you cut a sea star into individual pieces then each piece will become an individual organism N Parthenogenesis o The development of unfertilized eggs o Occurs in arthropods and some fish, amphibians and reptiles o Some species parthenogenesis determines sexhoney bees, males come from unfertilized eggs, females come from fertilized eggs www.notesolution.com
More Less
Unlock Document


Only pages 1-2 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


OR

Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit