A note on changing patterns of slave fertility in the South Carolina rice district, 1735-1865

Population size is dynamic, increasing with birth rates and immigration, and decreasing with death rates and emigration. In ideal conditions with unlimited resources, populations can increase exponentially, which plots as a J-shaped growth rate curve of population size against time. This type of curve is characteristic of newly-introduced invasive species, or populations that have suffered catastrophic declines and are rebounding.However, realistic environmental conditions limit the number of...

To determine whether traits are inherited together or separately, Gregor Mendel crossed pea plants that differed in two traits. These parental plants were homozygous for both traits but displayed different phenotypes. The first generation of offspring were all dihybrids, heterozygotes exhibiting the two dominant phenotypes. When self-fertilized, the dihybrids consistently produced progeny with a 9:3:3:1 ratio of four possible phenotype combinations. This ratio suggested that inheriting one...

In the 1850s and 1860s, Gregor Mendel investigated inheritance by performing monohybrid crosses in pea plants. He crossed two plants that were true-breeding for different traits. Based on his observations, Mendel proposed that organisms inherit two copies of each trait, one from each parent, and that dominant traits can hide recessive traits. These results formed the basis of two fundamental principles in genetics: the Principle of Uniformity and the Law of Segregation.Monohybrid Crosses Reveal...

Trihybrid Crosses
Some of Mendel’s crosses examined three pairs of contrasting characteristics. Such a cross is called a trihybrid cross. A trihybrid cross is a combination of three individual monohybrid crosses. For example, plant height (tall vs. short), seed shape (round vs. wrinkled), and seed color (yellow vs. green).
The F1 generation plants of a trihybrid cross are heterozygous for all three traits and produce eight gametes. Upon self-fertilization, these gametes have an equal chance to...

Constrained by limited energy and resources, organisms must compromise between offspring quantity and parental investment. This trade-off is represented by two primary reproductive strategies; K-strategists produce few offspring but provide substantial parental support, whereas r-strategists produce much progeny that receives little care. These strategies are related to an organism’s survival likelihood across its lifespan, which is represented by a survivorship curve. Three general types of...

Crop cultivation has a long history in human civilization, with records showing the cultivation of cereal plants beginning at around 8000 BC. This early plant breeding was developed primarily to provide a steady supply of food.