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