Anu SinghCundy Gary Shin Discover Biology SIXTH EDITION
Anu Singh-Cundy • Gary Shin Discover Biology SIXTH EDITION Unit 2 Genetics Extreme Biology supplemental slides © 2015 W. W. Norton & Company, Inc.
CHAPTER 9 Patterns of Inheritance
Key Concept: A phenotype is the specific version of a genetic trait that is displayed by a particular individual.
The Ultimate Phenotype • The display of a particular version of genetic trait in an individual is the phenotype of that individual. • Some genetic traits are invariant or nearly invariant, meaning they are about the same in all individuals in the population. Other traits are quite variable. • Many phenotypes are the result of the variant genotypes and the interaction of the environment. • Single nucleotide polymorphisms (SNPs), which are copying errors in the DNA, can also affect your phenotype.
Key Concept: Homozygotes are individuals that carry two of the same allele for a particular gene.
Homozygosity versus Heterozygosity • Mendel used the terms “true-breeding” and “hybrid” for homozygosity and heterozygosity, the terms we use today. • In dogs, a purebred would be a good example of a homozygous individual, and a mutt would be a good example of a heterozygous individual. • Purebred dogs have many known problems that are a result of homozygosity. For examples, German shepherds display hip dysplasia, Dalmatians display deafness, and poodles display eye disease. • Mutts can exhibit the same diseases, but are generally known for their “hybrid vigor, ” which is in part due to their heterozygosity.
CHAPTER 10 Chromosomes and Human Genetics
Key Concept: According to the chromosome theory of inheritance, genes are located on chromosomes, which pass from parent cell to daughter cell during cell division. Although chromosome number is species specific, the number of chromosomes is not correlated to the complexity of the organism.
Chromosome Numbers • Chromosome number is species specific, but does not define the species. For example, the normal human chromosome number is 46, but there are humans with 45 or 47 chromosomes. • Polyploidy, or having more than two sets of chromosomes, is common in plants and relatively rare in animals. • Scientists did not correctly determine the number of human chromosomes until 1956.
Key Concepts: The chromosomes that determine sex in humans are the sex chromosomes, X and Y. The XY combination confers maleness, and the XX combination leads to female characteristics. The other 22 chromosome pairs are autosomes. The SRY gene, found on the Y chromosome, is a key gene for the development of male sexual characteristics.
Chromosomal Legacies • Each individual bears the legacy of their parents’ chromosomes. The Y chromosome, passed from fathers to sons, is one of the simplest direct legacies to follow. • Genghis Kahn is not the only notable male with an extreme legacy. Giocangga, another Asian ruler, and Ui Neill, an Irish ruler, both have impressive legacies. • Having a legacy not only means that one man has many sons. Those sons must also have many sons, and the pattern must continue.
Anu Singh-Cundy • Gary Shin Discover Biology SIXTH EDITION Unit 4 The Biosphere Extreme Biology supplemental slides © 2015 W. W. Norton & Company, Inc.
CHAPTER 25 Global Change
Key Concept: The main cause of the current high rate of species extinctions are likely human activities that transform Earth’s land water.
Deforestation • Forests cover approximately 31 percent of the land on Earth. • Forests provide oxygen and serve as a carbon “sponge, ” soaking up excess carbon that would otherwise build up in the atmosphere and add to ongoing climate change. • The major threat to forests is deforestation. • Deforestation is a result of fire, clear-cutting, and unsustainable harvesting of trees. • Deforestation is a particular danger to rain forests as they contain much of the Earth’s biodiversity. • In the Amazon rainforest almost 17 percent of the biodiversity has been lost in the last 50 years, mainly due to clear-cutting for cattle ranching.
Key Concept: The main causes of the current high rate of species extinctions are likely human activities that transform Earth’s land water.
Ice Cores • Ice cores provide detailed information on past atmospheric conditions, including CO 2 levels. • Frozen precipitation can collect pollutants, gases, dust, and salt. • Analysis of this collection can provide details on past climates from a season past, to thousands of years past. • Ice cores mainly are drilled in Greenland in Antarctica.
Key Concept: The warming of Earth’s climate has led to melting of polar and glacial ice, rising sea levels, acidification of the oceans, and shifts in where many species live.
Receding Arctic Ice Cap • A 2012 NASA study found that the thicker ice, known as multiyear ice, is melting faster than the thinner, single-year ice. • Ice caps contain an enormous amount of frozen water. If this water melts, worldwide sea levels could rise several meters or more. • The melting of the Arctic ice cap reached record highs in 2008– 2012. The ice cap seems to be making a comeback, but scientists fear that the ice cap is still vulnerable after the loss of the older, thicker ice.
- Slides: 19