ASU BIO 182 EXAM 2
asexual reproduction
directing cells to divide and develop into new tissues and organs without a partner
sexual reproduction
-takes more time and energy than asexual reproduction
-genetically diverse offspring
-requires fertilization
-requires haploid gametes
-mating
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ASU BIO 182 EXAM 2
asexual reproduction
directing cells to divide and develop into new tissues and organs without a partner
sexual reproduction
-takes more time and energy than asexual reproduction
-genetically diverse offspring
-requires fertilization
-requires haploid gametes
-mating
most plants and animals produce_______
gametes called eggs and sperm
Meiosis
nuclear division that forms haploid cells
Meiosis I
diploid cells divide to create 2 haploid cells, each with one of the homologous
chromosomes
Meiosis II
2 haploid cells divide to form 4 haploid cells, which develop into eggs or sperm
Prophase I (Meiosis)
-chromosomes condense
-nuclear envelope breaks down
-spindle fibers start to form (microtubules)
-crossing over occurs
Metaphase 1 (Meiosis)
Pairs of homologous chromosomes move to metaphase plate
Anaphase I (Meiosis)
homologous chromosomes separate and move to opposite poles of the cell
Telophase and Cytokensis (Meiosis)
-chromosomes gather at poles of the cell
-cytoplasm divides
Prophase II (Meiosis)
-2 cells
-a new spindle forms around the chromosomes
Metaphase II (Meiosis)
chromosomes line up at the metaphase plate/equator
Anaphase II (Meiosis)
-2 cells
-centromeres divide
-chromatids move to opposite poles of the cells
Telophase II and Cytokinesis (Meiosis)
-goes from 2 cells to 4 cells
-nuclear envelope forms around each set of chromosomes
-cytoplasm divides
Asexual organisms
, -New alleles must occur independently
-can't be passed around and mixed with the genetic make up/ different alleles of other
organisms
Sexual organisms
-populations can accrue new beneficial alleles in a shorter period of time than asexual
organisms
-organisms in a population can share beneficial alleles
-takes all the best alleles and puts them in a "basket" that selection can favor
sex creates_____
-genetic variation among offspring
-allows populations to adapt to environmental change faster
organisms in more variable environments______
-show a higher propensity (a preference) for sexual reproduction compared to asexual
-could be due to increase in genetic variation to increase rate of adaptation to the
environment
linked alleles/genes
-genes are close together on the same chromosome
-breaks the law of independent assortment
-genes closer to each other on a chromosome are less likely to recombine during
crossover
crossing over enables_____
an organism to recombine alleles on the same chromosome with alleles on a
homologous chromosome
genetic drift
-a process through which populations evolve randomly
-by chance, some individuals have more offspring than others
-smaller populations evolve rapidly
Bottleneck effect
-loss of genetic diversity following a sudden drop in a population
-can occur in a single generation
genetic drift occurs when_____
a portion of the population dispersed to a new habitat/ becomes separated by a physical
barrier
founder effect
-loss of alleles that occur when individuals start a new, smaller population
-increases chances of genetic disorder
natural selection
-causes phenotypes to evolve in a particular direction
-requires repeatable differences in reproductive success among genotypes
-always causes adaptation of a trait
-most important mechanism of evolution in large populations
Genetic drift
-has a large effect on allele frequency in small populations/ small effect on large
populations
-requires random differences in reproductive isolation to evolve between geographically
isolated sub-populations
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