Biology Keystone Remediation Evolution

Biogenesis Biogenesis states all living things come from other living things. Before the seventeenth century it was believed that living things could arise from nonliving things Spontaneous generation

Redi’s Experiment Francesco Redi (1626-1697) Disproved that flies generated spontaneously from rotting meat. Observed the life cycle of flies. He noted that maggots appeared where flies had landed, they turned into pupas and then to flies. Experiment with open container with rotten meat (experimental) and closed container with rotten meat (control).

Spallanzani’s Experiment Lazzaro Spallanzani (1729-1799) Designed an experiment using a microscope and broth to disprove spontaneous generation of microorganisms. Not everyone considered is experiment valid. They believed the heating was not the same for all samples. image

Pasteur’s Experiment Louis Pasteur (1822-1895) The Paris Academy of Science offered a prize to anyone who could end the spontaneous generation controversy. Pasteur’s experiment won Curve-necked flask was used. This allowed for air flow, but kept out solid particles Broth was boiled and let stand No grow for up to a year Neck was broken and growth occurred within a day. Spontaneous generation was disproved.

Earth’s History Earth is approximately 4.6 billion years old Based on studies of Earth’s surface and the use of radiometric dating. First Organic Compounds Synthesized from the Earth’s early atmosphere along with a spark (lighting) Cell-Like Structures Microspheres-spherical in shape, composed of protein molecules Coacervates-collection of droplets composed of lipids, amino acids and sugars Form spontaneously in the laboratory Have many of the same properties of life, expect for the hereditary characteristics.

The First Cells It is believed that the first type of cells to evolve where anaerobic, heterotrophic prokaryotes (anaerobic – live without oxygen, heterotrophic-consume to get food, prokaryotes – single cell with no membrane bound organelles or nucleus Feed on the organic molecules from their surrounding environment Eventually these molecules would be gone and the first autotrophs evolved.

Chemosynthesis Autotroph that obtains energy from oxidizing inorganic compound Archea – unicellular organisms that strive in extremely harsh environments Believed to be very similar to the first autrophs to evolve about 4 million years ago. Methanosarcina barkeri Produces methane during its metabolism

Photosynthetic Autotrophs About 3 million years ago the first photosynthetic organisms evolved. Similar to modern cyanobacteria Oxygen is a by product of photosynthesis and changed the make up of the Earth’s atmosphere

The First Eukaryotes Features of eukaryotes evolved from prokaryotes The ER and nuclear envelope formed from the infolding of the plasma membrane of a prokaryote Lynn Margulis Endosymbiosis – eukaryotic cells evolved from a mutually beneficial relationship between primitive eukaryote and the prokaryote it engulfed. Mitochondria and chloroplasts Replicate independently and contain some of their own genetic material similar to prokaryotes

Theory of Evolution Charles Darwin (1823-1882) developed his theory while sailing around the world on the HMS Beagle Galapagos Islands Evolution – the development of new types of organisms from preexisting types of organisms over time; the change in the characteristics of a population over time

Ideas of Darwin’s Time Species were permanent and unchanging Jean Baptiste Lamarck (1744-1829) Inheritance of acquired characteristics – individuals could acquire traits during their lifetime as a result of experience or behavior, then could pass on those traits to offspring.

Darwin’s Ideas On the Origin of Species by Means of Natural Selection was published in 1859 a year after Darwin presented his research in London His theory was supported by a large amount of evidence He used the phrase descent with modification to help explain evolution Species descend by reproduction from preexisting species He was the first to argue that all species originate this way Galapagos Finches (Darwin’s Finches)-13 species

Natural Selection Survival of the Fittest Natural Selection - Mechanisms of evolution Overproduction of offspring More offspring are produced than can survive Genetic Variation Individuals have different traits Struggle to Survive Competition for resources Differential Reproduction Organisms with the best adaptation are most likely to survive and reproduce. Survival of the Fittest

Evidence to Support Evolution The Fossil Record Types and distribution of organisms on Earth have changed over time. Fossils of transitional species show evidence of descent with modification

Evidence to Support Evolution Biogeography Distribution of organisms, shows evidence of descent with modification Animals that are closely related, but adapted to different environments Animals that seem unrelated but have similar adaptations to similar environments

Evidence to Support Evolution 3. Anatomy Homologous structures- anatomical structures that occur in different species and that originated by heredity from a common ancestor Similar bone structure of forelimbs in humans, penguins, alligators, and bats

Evidence to Support Evolution 3. Anatomy B. Analogous Structures-closely related functions by do not derive from the same ancestral structure Wings of birds, bats, and moths Similar in function, but not in structure

Evidence to Support Evolution 3. Anatomy C. Vestigial Structures-serve no function but that resemble structures with functional roles in related organisms Human tailbone(coccyx)- four fused vertebrae that resemble the bones in an animals tail Pelvic bones of modern whales and the human appendix

Evidence to Support Evolution 4. Embryology Stages of a vertebrate embryo development are very alike In early development this fades further into development

Evidence to Support Evolution 5. Biological Molecules Modern scientists have shown that similarity in subunit sequences of RNA, DNA, and proteins indicates a common evolutionary history. Approximately 98% of our DNA is similar to the DNA of a chimpanzee.

Evolution in Action

Evolution in Action Evolution is a continuous process and can be observed, recorded and tested today. New species arise from environmental pressure and interactions with other species including humans.

Convergent Evolution Convergent evolution- process by which different species evolve similar traits. They live in similar ecosystems and have similar pressures. Similar but Separate –while they may look similar their evolution occurred independently of one another. Bird and bat wings.

Divergent Evolution Divergent Evolution- process by which descendants of a single ancestor diversify into species that fit different parts of the environment. Anole lizards twig-dwelling and trunk-dwelling Sometimes, a new population in a new environment, such as an island, will undergo divergent evolution until the population fills many parts of the environment. This pattern is known as adaptive radiation Darwin’s finches.

Artificial Selection Artificial selection – when a human breeder chooses individuals that will parent the next generation. Dogs

Coevolution Coevolution – when two or more species have evolved adaptation to each other’s influence Together, but Different Acacia tree and acacia ant

Population Genetics

Genetic Equilibrium Population biologists study many different traits in populations, such as size and color. Traits vary and can be mapped along a bell curve, which shows that most individuals have average traits, whereas a few individuals have extreme traits. Variation in genotype arise by mutation, recombination, and the random fusion of gametes. The total genetic information available in a population is called the gene pool

Genetic Equilibrium Allele frequencies in the gene pool do not change unless acted upon by certain forces. The principle of Hardy-Weinberg genetic equilibrium is a theoretical model of population in which no evolution occurs and the gene pool of the population is stable Genotype frequencies in a population tend to remain the same from generation to generation unless acted on by outside influences.

Disruption of Genetic Equilibrium Evolution can take place when a population is not in a state of genetic equilibrium. Thus, evolution may take place when populations are subject to genetic mutations, gene flow, genetic drift, nonrandom mating, or natural selection. Emigration and immigration cause gene flow between populations and can thus affect gene frequencies. Genetic drift is a change in allele frequencies due to random events. Genetic drift operates most strongly in small populations.

Disruption of Genetic Equilibrium Mating in nonrandom whenever individuals may choose partners. Sexual selection occurs when certain traits increase an individual’s success at mating. Sexual selection explains the development of traits that improve reproductive success but may harm the individual. Natural selection can influence evolution in one of three general patterns. Stabilizing selection favors the formation of average traits. Disruptive selection favors the extreme traits rather than the average traits. Directional selection favors the formation of more-extreme traits.

Formation of Species According to the biological species concept, a species is a population of organisms that can successfully interbreed but cannot breed with other groups. (must produce fertile offspring) Geographic isolation results from the separation of population subgroups by geographic barriers. Geographic isolation may lead to allopatric speciation. Two closely related squirrels found on opposite sides of the Grand Canyon.

Formation of Species Reproductive isolation results from the separation of population subgroups by barriers to successful breeding. Reproductive isolation may lead to sympatric speciation. Competing individuals within a population could gain an adaptive advantage by using slightly different niches. Which could lead to the groups becoming reproductively isolated. Darwin’s finches.

Formation of Species In the gradual model of speciation, species undergo small changes at a constant rate. In the punctuated equilibrium model, new species arise abruptly, differ greatly from their ancestors, and then change little over long periods.