TOPIC 4

EVOULUTION OF SEX & REPRODUCTIVE PATTERNS

A. REPRODUCTION VERSUS SEX

B. TYPES OF CELL DIVISION

1. BINARY FISSION

2. MITOSIS

3. MEIOSIS

C. EUKARYOTIC LIFE CYCLES

1. TERMS

2. 3 SEXUAL LIFE CYCLES

 

A. REPRODUCTION VERSUS SEX

REPRODUCTION = INCREASE IN THE NUMBER OF INDIVIDUALS

SEX = EXCHANGE OF GENETIC MATERIAL BETWEEN INDIVIDUALS

2 PARENTS PRODUCE AN OFFSPRING

OFFSPRING HAS A COMBINATION OF GENES INHERITED FROM EACH

PARENT

 

REPRODUCTION WITHOUT SEX

= ASEXUAL REPRODUCTION OFFSPRING IDENTICAL TO PARENT

SEEN IN ALL KINGDOMS

 

SEX WITHOUT REPRODUCTION

CONJUGATION

TRANSFER OF DNA BETWEEN SINGLE CELLS

DONOR & RECEIVER OR MUTUAL EXCHANGE

SEEN IN PROKARYOTES & PROTISTS

 

ADVANTAGES OF SEX?

GENETIC DIVERSITY OF OFFSPRING

 

MOST IMPORTANT WHEN ENVIRONMENT VARIES & VARIABILITY CAN NOT BE

PREDICTED

 

ADVANTAGES OF EUKARYOTIC SEX INVOLVING DIPLOIDY?

DIPLOID CELLS HAVE INSURANCE AGAINST MUTATION IF 1 COPY OF GENE DAMAGED = SECOND AVAILABLE

 

DIPLOID CELLS ARE MORE VERSATILE OFTEN HAVE 2 DIFFERENT VERSIONS OF GIVEN GENE

OFTEN BOTH PRODUCE PRODUCTS

 

DIPLOID CELLS CAN PRODUCE GENETICALLY DIVERSE OFFSPRING THRU:

INDEPENDENT ASSORTMENT OFCHROMOSOMES DURING MEIOSIS

CROSSING-OVER DURING MEIOSIS

 

B. TYPES OF CELL DIVISION

1. BINARY FISSION

IN PROKARYOTES

ONLY FORM OF REPRODUCTION

1 HAPLOID CELL (1n) = > 2 HAPLOID CELLS (1n)

 

2. MITOSIS

ONLY IN EUKARYOTES

PROCESS OF NUCLEAR DIVISION THAT CONSERVES CHROMOSOME NUMBER

1 DIPLOID CELL (2n) = > 2 DIPLOID CELLS (2n)

1 HAPLOID CEL (1n) = > 2 HAPLOID CELLS (1n)

 

UNICELLULAR EUKARYOTES

USED FOR REPRODUCTION

 

MULTICELLULAR EUKARYOTES

USED FOR GROWTH, DEVELOPMENT, & MAINTENANCE

USED FOR ASEXUAL REPODUCTION

VEGETATIVE REPRODUCTION

SPORE PRODUCTION

SPORE = SINGLE CELL REPRODUCTIVE PROPAGULES

(1n or 2n) = > MULTICELLULAR INDIVIDUALS

HAPLOID (1n) OR DIPLOID (2n)

 

USED IN SEXUAL CYCLES

HAPLOID INDIVIDUAL (1n) PRODUCES GAMETES (1n)

 

3. MEIOSIS

ONLY IN UNICELLULAR & MULTICELLULAR EUKARYOTES

ONLY IN DIPLOID CELLS (2n)

SEXUAL REPRODUCTION ONLY

NUCLEAR DIVISION IN 2 STAGES

= INITIAL CHROMOSOME NUMBER HALVED

1 DIPLOID CELL (2n) = > 4 HAPLOID CELLS (1n)

PRODUCE GAMETES (1n) = >

2 GAMETES FUSE = > DIPLOID ZYGOTE (2n)

PRODUCE SPORES (1n) = >

MULTICELLULAR HAPLOID INDIVIDUAL (1n)

 

C. EUKARYOTIC LIFE CYCLES

1. TERMS ASSOCIATED WITH SEXUAL LIFE CYCLES

 

CHROMOSOME NUMBER

HAPLOID (1n)

DIPLOID (2n)

 

REPRODUCTIVE PROPAGULES

SPORE (1n or 2n)

GAMETE (1n)

ISOGAMY = 1 TYPE OF GAMETE

ANISOGAMY = 2 TYPES OF GAMETES

LARGE, NOMOTILE OVUM (EGG)

SMALL, MOTILE SPERM

 

UNION OF GAMETES

SYNGAMY = FUSION OF 2 HAPLOID CELLS = FERTILIZATION

PRODUCES ZYGOTE (2n)

OCCURS IN 2 STAGES

PLASMOGAMY = FUSION OF CYTOPLASM

KARYOGAMY = FUSION OF NUCLEI

IF STAGES ARE SEPARATED IN TIME

DIKARYOTIC CELLS = 2 HAPLOID NUCLEI

COMMON IN FUNGI

C. EUKARYOTIC LIFE CYCLES

 

 

2. 3 SEXUAL LIFE CYCLES OF MULTICELLULAR ORGANISMS

DIFFER BASED ON TIMING OF MEIOSIS & FERTILIZATION

PROMINENCE OF HAPLOID VERSUS DIPOLOID STAGES

INCLUSION OF STAGES INVOLVING ASEXUAL REPRODUCTION

 

 

DIPLONTIC LIFE CYCLE

MULTICELLULAR DIPLOID PHASE OF THE LIFE CYCLE DOMINATES

IN SIZE, COMPLEXITY & DURATION

ONLY HAPLOID PHASE = GAMETES = SINGLE CELLS

MEIOSIS GIVES RISE TO GAMETES

HAPLOID GAMETES FUSE TO FORM DIPLOID ZYGOTE

ZYGOTE DIVIDES VIA MITOSIS

GIVES RISE TO MULTICELLULAR DIPLOID ORGANISM

DIPLOID FORM EVENTUALLY PRODUCES HAPLOID GAMETES

VIA MEIOSIS

FOUND IN ANIMALS

 

 

HAPLONTIC LIFE CYCLE

MULTICELLULAR HAPLOID PHASE OF THE LIFE CYCLE DOMINATES

IN SIZE, COMPLEXITY & DURATION

ONLY DIPLOID PHASE = SINGLE CELL = ZYGOTE

HAPLOID GAMETES FUSE TO FORM DIPLOID ZYGOTE

ZYGOTE SOON UNDERGOES MEIOSIS TO FORM HAPLOID SPORES

SPORE DIVIDES VIA MITOSIS

GIVES RISE TO MULTICELLULAR HAPLOID ORGANISM

HAPLOID FORM EVENTUALLY PRODUCES HAPLOID GAMETES VIA MITOSIS

FOUND IN FUNGI, CELLULAR SLIME MOLDS, & SOME ALGAE

 

 

ALTERNATION OF GENERATIONS

MULTICELLULAR DIPLOID & HAPLOID PHASES OCCUR IN THE LIFE CYCLE

PHASES VARY IN SIZE, COMPLEXITY & DURATION

HAPLOID GAMETES FUSE TO FORM DIPLOID ZYGOTE

ZYGOTE DIVIDES VIA MITOSIS

GIVES RISE TO MULTICELLULAR DIPLOID ORGANISM = SPOROPHYTE

SPOROPHYTE EVENTUALLY PRODUCES HAPLOID SPORES VIA MEIOSIS

SPORE DIVIDES VIA MITOSIS

GIVES RISE TO MULTICELLULAR HAPLOID ORGANISM = GAMETOPHYTE

HAPLOID FORM EVENTUALLY PRODUCES HAPLOID GAMETES VIA MITOSIS

IF HAPLOID & DIPLOID FORMS SIMILAR IN MORPHOLOGY = ISOMORPHIC

IF HAPLOID & DIPLOID FORMS DIFFER IN MORPHOLOGY = HETEROMORPHIC

FOUND IN PLANTS & SOME ALGAE