Theorists and Evidence - AP Biology

Gregor Mendel studied genetics through the crossbreeding of pea plants. Through his studies, he proposed laws of heredity (the law of segregation, the law of independent assortment, and the law of dominance), that are now called the laws of Mendelian inheritance. Darwin famously studied finches on the Galapagos Islands.

Evolution is any change in the proportions of different genotypes in a population from one generation to the next. Mutation, geneflow, nonrandom mating, and natural selection all contribute toward favoring certain alleles over others within a population. This leads to changes in allele frequency, and subsequent evolution.

It is believed that sponges were the first animals to utilize multicellularity. Sponges only have a few cell types, including: choanocytes, porocytes, and pinacocytes. Choanocytes have flagella that beat continuously to move water, and microvilli, which are specialized for absorbing nutrients. Porocytes are tubular cells that form the pores of sponges. Pinacocytes produce collagen and provide structural support to the sponge. Although algae likely developed multicellularity early on, they are not animals. Arthropods and mammals are both multicellular and animals, but evolved after sponges.

Lamarck incorrectly believed that parents could pass on traits that they had acquired to their offspring. He believed that the changes made during a lifetime, such as increased muscle mass, would be passed on to offspring. This is not true since acquired traits, except on very few rare occasions, do not affect the DNA. For example, if two parents have small muscles, but then take steroids and become bodybuilders, their offspring will still inherit the small muscle genes, since only the muscles, not the DNA is affected by bodybuilding.

When a thermal neutron collides with a nitrogen atom in the atmosphere, it causes a proton to fly off from the atom, reducing the atom from nitrogen to carbon while keeping the same number of neutrons, 14. Because the amount of matter in the universe is believed to be constant, we can measure the amount of carbon-14 left in a dead specimen to determine its age within approximately 50,000 years.

Coprolites are fossilized fecal matter from an animal. By studying their contents, biologists can gather information on what the animal ate, and what species were there to be eaten by the animal.

Carbon-14 dating is used to date organic material within an approximately 50,000 year time period, due to the relatively short half life of the carbon-14 isotope. Other isotopes are used to date the rocks surrounding dinosaur fossils, such as in the uranium-lead method or the potassium-argon method.

The key to answering this question is organic material. Once an organism dies, it ceases to participate in carbon exchanges with the atmosphere. What carbon is left in the organism then decreases at a stable rate which allows scientists to reliable date the era that the organism died in.

Lamarck theorized that animals evolved into new forms based on need or utility, and thus he is the correct answer for this question.

Darwin was the father of the theory of evolution by natural selection (along with Alfred Russell Wallace), Watson and Crick discovered the structure of DNA (along with Rosalind Franklin), Leeuwenhoek pioneered microscopy, and Jonas Salk created the polio vaccine, so none of those are correct.

The principal of use and disuse suggests that organs you use get bigger while those you don't use get smaller or even disappear entirely. Inheritance of acquired characteristics sugegsts that proficiencies and traits can be passed down to succeeding generations. Lamarckian evolution is largely based on these two ideals.

Theory of genetic chance is not a real foundation of Lamarckian evolution.

While Lamarck had many revolutionary ideas on evolution, his most correct assumption was the importance of environmental changes on evolutionary adaptations. His theories on the inheritance of acquired traits and essentialsm do not fit into our current knowledge of evolution, DNA, and inheritance.

The theory of inheritance of acquired characteristics was one of the earliest theories of evolution. Lamarck believed that traits were passed down to offspring when the parent showed increased use of those traits, and that traits that were not used by the parent were not inherited. The most common example of this "use and disuse" idea was a giraffe that, during its lifetime, often stretched its neck to reach leaves, and thus had a greater number of offspring with long necks.

This theory was shown to be incorrect in favor of Darwin's theory of evolution by natural selection. Use or disuse during an organism's lifespan is not the driving force of evolution.

Lamarck hypothesized, amongst other things, that organisms could pass down traits acquired during life from generation to generation. Under Lamarck's theory of use and disuse, a man who worked in a factory and developed strong arms would pass the strong arms trait to his offspring. This hypothesis has largely been rejected by modern genetics.

Gregor Mendel is the founder of modern genetics, developing our modern understanding of allelic inheritance. Charles Darwin developed important theories about evolution and natural selection. Carolus Linnaeus is best remembered for establishing binomial nomenclature, the system used today to officially name organisms.

Jean-Baptiste Lamarck was an evolutionary theorist who was rejected by Charles Darwin. In his theory, Lamarck supported the idea that individuals could pass down acquired characteristics to their offspring, and that they lost un-needed traits and gained useful traits. The most recent theory of evolution, like Charles Darwin, rejects these claim.

Gregor Mendel's famous work on pea plants built our first understandings of inheritance. He identified that "discrete particles", which we now call genes and alleles, are passed to offspring in numerous of combinations. These different combinations create variation in a population.

Mendel is considered the father of modern genetics and did extensive research on genetic heritability, alleles, and inheritance. His main research was performed on drosophila (flies) and pea plants. Mendel's discoveries helped shape our understanding of how genes are inherited and expressed. One of his theories outlines the idea that chromosomes do not align by paternal and maternal segregation during tetrad formation in meiosis, but are organized independent of their parental origin. This theory is known as the Principle of Independent Assortment.

The Law of Population Genetics was developed by Hardy and Weinberg. Charles Darwin created the Theory of Evolution. Lamarck created the Postulate of Inheritance of Acquired Traits.

Mendel's "factors" are today's genes. From his limited knowledge of cell biology, Mendel was able to observe the effects of genes by observing phenotype. Genes come in multiple forms, known today as alleles, which control dominant and recessive inheritance.

Chromatin is the term used to describe DNA packaged by proteins. Centromeres are the area of chromosomes where sister chromatids are attached. Chromosomes would not be an acceptable description of a "factor" because it is the specific gene that controls the phenotype, not the entire chromosome.

Pea plants reproduce quickly and in large numbers. They can self-pollinate within a single plant, they can be cross-pollinated by insection, and they can be selectively cross-pollinated using a tool such as a cotton swab. Pea plants contain separate male and female parts, but each plant contains both. Sex-linked traits cannot be studied in organisms that do not have clearly separate male and female members. Phenotypically, there are no male and female members of the pea plant species, making it impossible to track traits that follow sex-linked expression.

Cystic fibrosis occurs in individuals who are homozygous recessive for a single gene, following Mendelian inheritance patterns.

Down Syndrome is caused by a trisomy and is not conferred via a specific allele. The disorder is the result of a nondisjunction event during meiosis. Fragile X Syndrome occurs when a portion of the X-chromosome in men is extended due to dozens or hundreds of repeats. The number of repeats changes between generations, making this non-Mendelian. Type I diabetes is most often caused by a poorly understood autoimmune condition, wherein the immune system attacks the cells in the pancreas responsible for insulin production. The underlying autoimmune response is thought to be partially genetic and partially environmental.

Genes are determined by sequences of DNA that code for certain proteins. Sometimes, mutations to the gene can result in a modified protein that maintains the same or similar functions as the original. When this modified gene is passed down, it is known as an allele. Most accurately, an allele is a variation of a given gene.

Most alleles can be considered dominant or recessive, with respect to one another; however, instances of codominance and incomplete dominance mean that there is a spectrum of dominance. Defining all alleles by these parameters is not very accurate. Some alleles code for wild genotypes, while others code for mutated genotypes. Recombination is the transfer of genetic material between homologous chromosomes, and does not result in new alleles. New alleles require a mutation event in order to increase genetic diversity.