BIO 102_SYSTEMATICS MIDTERMS T3

• Genetic variation is the raw material of evolution.
• A major characteristic that allows organisms to survive in changing conditions is variation.
• Types of Biological Variation: Individual, Group, Non-genetic, Genetic Variation
• Individual Variation - differences among individuals of a single population
• Group Variation - differences among populations
• Non-genetic variation - act on individual
• Genetic variation - act on both individual and the population
• Individual Variation - the members of a population share some important features but differ from one another in numerous ways
• Individual variations: Seasonal, Habitat, Allometric, Neurogenic/Neurohormonal. Age, Parasite-induced, Social
• Age Variation - differences on the basis of age clusters or between immatures or larvae, juveniles and adults.
• In age variation, it is an advantage for the species when the immatures occupy a different niche from that of the adults.
• In age variation - age group must be adapted for the specific role it plays in the life cycle in the performance of special states, such as dispersal, growth and reproduction.
• Seasonal Variation - adult individuals of certain species are subject to seasonal changes in phenotype
• Social variation - division of labor (insect castes) in insect societies is based on major biological differences between individuals
• Allometric growth may result in the disproportionate size of some structures in relation to that of the rest of the body.
• Allometry refers to the relationship of body size to shape, anatomy, physiology and finally behaviour of an organism
• Habitat Variation - the direct effect of the physical environment on the phenotype
• Ecophenotype results from modification by edaphic (substrate) or other ecological conditions, and not from changes in the genotype.
• Among animals, the effect of environment is evident in sessile marine invertebrates like sponges and corals and in some mollusks
• Neurogenic/Neurohumoral Variation - color change in individual species in response to the environment
• The changes are accomplished through the concentration or dispersal of color-bearing bodies known as chromatophores.
• Parasite induced variation - parasites may produce conspicuous structural modifications such as swelling, distortion, and mechanical injury
• Sex differences - individual differences of organisms involving sexual characteristics
• Sexual Dimorphism- differences between male and female individual
• Cyclical parthenogenes- alternation of one or many generations of asexual reproduction with a single generation of sexual reproduction.
• Species that produce both sexual and asexual morphs are holocylic. Both asexual and sexual morphs are produced at different times of the year
• Aphidomorpha- Aphids, green flies, plant lice.
• Fundatrix: a viviparous parthenogenetic winged or wingless female aphid
• Aphids can accomplish this feat because they have an XO sex determining mechanism.
• Anholocyclic species only produce asexual females.
• A gynandromorph individual has one part of its body male while the other part has female characters.
• Gynandromorphism results from an unequal somatic distribution of chromosomes, particularly sex chromosomes.
• Gynandromorph- two halves of the body are of opposite sex or sex characters maybe scattered in a mosiac.
• Aneuploidy is an abnormal number of chromosomes, either extra or missing chromosome.
• Intersexes exhibit a blending of male and female characters
• Intersexes is generally thought to result from an upset in the balance in fertilization or mitosis or from physiological disturbance associated with parasitism.
• The occurrence of differences among segregated populations of a species is called geographic variation.
• Local variation among neighboring populations is termed “microgeographical” variation
• Populations from different portions of the range of a species differ from each other by “gradual” characters, and that these differences should be greater the greater the distance.
• Hybridization is evident between most adjacent populations, but studies of variation in proteins and DNA show large amounts of genetic divergence among populations