Chapter 7 Section 2: Sexual Reproduction Grade 10 Biology Fall 2010.
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Transcript of Chapter 7 Section 2: Sexual Reproduction Grade 10 Biology Fall 2010.
Chapter 7Section 2: Sexual Reproduction
Grade 10 BiologyFall 2010
Objectives•Differentiate between asexual and sexual
reproduction•Identify three types of asexual
reproduction•Evaluate the relative genetic and
evolutionary advantages and disadvantages of asexual and sexual reproduction
•Differentiate between the three major sexual life cycles found in eukaryotes
Sexual and Asexual Reproduction•Reproduction: the process of producing
offspring, can be asexual or sexual
Sexual and Asexual Reproduction•Asexual reproduction: single parent
passes copies of all of its genes to each of its offspring ▫No fusion of haploid cells such as gametes
•Clone: individual produced by asexual reproduction, genetically identical to its parents
•Example: prokaryotes, binary fission ▫Do eukaryotes reproduce asexually?
Asexual Reproduction
Prokaryotes Eukaryotes
Sexual and Asexual Reproduction•Sexual reproduction: two parents each
form reproductive cells that ave one-half the number of chromsomes ▫Haploid gametes form diploid offspring▫“2 halves make a whole”
•Offspring have traits of both parents•Occurs in eukaryotes
Sexual Reproduction
Types of Asexual Reproduction•Fission:
separation of a parent into two or more individuals of about equal size ▫Prokaryotes
Types of Asexual Reproduction•Fragmentation: body breaks into several
pieces, fragments develop into complete adults▫Eukaryotes
Types of Asexual Reproduction•Budding: new individuals split off from
existing ones ▫Eukaryotes
Genetic Diversity•Asexual reproduction •Advantages:
▫Simplest and most primitive method of reproduction
▫Allows organism to produce many offspring with less energy
•Disadvantages:▫DNA varies little between individuals ▫Less adaptation abilities
Genetic Diversity•Sexual Reproduction:•Advantages:
▫Genetic variation •Disadvantages:
▫Takes more time and energy
Sexual Life Cycle in Eukaryotes•Life cycle: entire span in the life cycle of
an organism from one generation to the next
•Eukaryotes that undergo sexual reproduction can have one of three types of sexual life cycles:▫Haploid ▫Diploid ▫Alternation of generations
Haploid Life Cycle•Simplest of sexual life cycles •Haploid cells occupy the major portion of
the life cycle •Zygote: only diploid cell, undergoes
meiosis immediately after it is formed •Haploid cells give rise to haploid
multicellular individuals that produce gametes by mitosis (not meiosis)
•Process called fusion, gametes fuse to produce a diploid zygote, cycle continues
Haploid Life Cycle
Diploid Life Cycle•Adult individuals are diploid•Individuals inherit chromosomes from 2
parents•Diploid reproductive cell undergoes
meiosis to produce gametes •Gametes (sperm and egg) join in
fertilization ▫Results in diploid zygote
Diploid Life Cycle
Alternation of Generations •Alternates between haploid and diploid
phase•Occurs in plants, algae, and some protists
Alternation of Generations •In plants:•Sporophyte: diploid phase in the life cycle
that produces spores•Spore: haploid reproductive cell produced
by meiosis that is capable of developing into an adult without fusing with another cell▫Spore gives rise to a multicellular individual
called a gametophyte without joining with another cell
Alternation of Generations •Gametophyte: haploid phase that
produces gametes by mitosis ▫Gametes fuse and give rise to the diploid
phase •Sporophyte and gametohpyte generations
take turns, or alternate, in life cycle