Life Cycle Summary Diploid Life cycle Haploid Life cycle Alternation of Generations Mitosis? Meiosis? Fertilization Mitosis after meiosis? Mitosis after fertilization? Multicellular diploid stage? Multicellular Haploid Stage? YesYes Yes NoYes Yes YesNo Yes NoYes Yes

Evolution: Classically: A change in the relative frequencies of heritable traits within a population across generations Relative frequency: 50% Tall plants 50% Short plants 55 generations later 25% Tall plants 75% Short plants Modern: A change in the distribution of relative frequencies of genes (which code for heritable traits) within a population across generations

Requirements for Evolution to occur: Variation in traits [via genes (alleles)] Heredity

Darwin’s Observations Biogeography: species are distributed in distinct clumps across the globe

Fossils Evidence of organisms no longer present

Evidence that many living organisms were not present in the past. Today 10,000 years ago 2 million years ago 5.5 million years ago 24 million years ago 34 million years ago Moeri- therium Bary-therium Deinotherium Mammut (mastodon) Platybelodon Stegodon Elephas maximus (Asian elephant) Mammuthus (mammoth) Loxodonta africana (African savannah elephant)

Agriculture: Selective breeding Ancestral Corn (genetically reconstructed) Modern Corn

Agriculture: Selective breeding

About 250 million years ago Plate tectonics Plate movements and geological studies indicated the earth was older than the estimated 6,000 years Figure Millions of years ago Cenozoic Mesozoic Paleozoic North America Eurasia South America Africa India Madagascar Antarctic Australia Laurasia Gondwana Pangaea

Economics: Competition for resources and the effects of overpopulation Struggle for existence

Evolution by Natural Selection (a mechanism of evolution) Population level: If variation existsand If variation is heritableand If differential reproduction (differential selection) exists Then over time, those variations that enhance the ablitiy of the organism to reproduce will increase in any population

Mutation occurs in the trait Mutation directly changes gene frequencies An example of a spontaneous mutation during the development of plant leaves For evolution to occur via this mechanism, what has to be true of the mutation? The mutation has to be heritable The mutation of fruit flies with four wings is an inherited mutation

The population size is small Genetic drift – random fluctuations in the allele frequencies Generation 1 p (frequency of R) = 0.7 q (frequency of r) = 0.3 Only 5 of 10 plant s leave offspr ing Generation 2 p = 0.5 q = 0.5 Only 2 of 10 plants leave offspri ng Generation 3 p = 1.0 q = 0.0

Gene flow Immigration or emigration occurs based on the trait

Sexual Selection Mating is non-random in the population with respect to the trait

Which mechanism leads to adaptation to the environment? Natural selection: Adaptations are traits that increase the probability that an organism will survive and reproduce in the current environmental conditions.

What is an adaptation? A heritable characteristic of an organism that helps it to survive and reproduce in a particular environment. Mimicry of a poisonous animal will increase the probability of survival and survival until the organism is able to reproduce

Example: Marine Iguana Adaptations do not have to be one trait, they can be a suit of traits “The guanas are small, and of a sooty black, which, if possible, heightens their native ugliness. Indeed, so disgusting is their appearance, that no one on board could be prevailed on, to take them as food.” Captain James Colnett (1798)

Flattened tail – aids in swimming Salt gland – Allows drinking of salt water Long, sharp claws – Aid in clinging to rocks Diving adaptations. While diving they: Reduce blood flow to body surface- helps retain heat Lower metabolic rate – conserves O 2

Adaptation refers to traits that are heritable Acclimation: Changes in the structure or physiology of an individual over its lifetime Examples: Increasing muscle mass via weightlifting High altitude acclimation:

Organizational level evolution occurs? Living organisms display a natural hierarchy of organization and emergent properties that are more than the simple sum of their parts Atoms lead to Molecules, which lead to Organelles, which are arranged within Cells, which make up Tissues, which make Organs, which form Organ systems, which together make an Organism, which is part of a Population within a Community in an Ecosystem, the largest of which is the Biosphere (=Earth)