Meiosis Video
D 36. Explain how meiosis contributes to the genetic variability of organisms.
Organisms in a population that reproduces sexually are not all alike. Differences among members of a population are collectively called variation. Variation results from the recombination of genes during meiosis and fertilization. Meiosis and fertilization shuffle the genes from parent organisms, producing new combinations of genes in the offspring.
Gregory Mendel's Work

D 37. Use the Punnet Square technique to predict the distribution of traits in mono- and di- hybrid crossings.

Monohybrid: One trait at a time

Dihybrid: A cross between two traits at the same time

genetics_as[1].jpgYs represet color - YY and Yy are yellow, and yy is green (Y = dominant y=recessive) Rs represent round RR and Rr are round and rr is wrinkled (R = dominant r = recessive)

D 38. Deduce the probable mode of inheritance of traits (e.g., recessive/dominant, sex-linked) from pedigree diagrams showing phenotypes.

Sex Linked Disorder Pedigree Diagram:


pedigree is a chart that shows how a trait, and the genes that control it, are inherited in a family.
Recessive Genetic Disorders are disorders that are inherited when the individual receives two recessive alleles (traits) that cause disorders from their parents. The parents might not have the disorder themselves, they might only carry the allele and have a dominant gene that dominates over it and cancels it out.
Dominant Genetic Disorders are disorders that are much less common than disorders caused by recessive alleles. It is caused by an inheritance of a dominating gene from the parents, one of which who has to have the disorder.
Sex Linked Genetic Disorders discriminate against a specific sex, such as color blindness in only males, and scoliosis in mostly females.

How to use and interpret a Pedigree Chart:

D 39. Describe the difference between genetic disorders and infectious diseases.

D39. An infectious disease is any illness caused by organism or viruses that enter and reproduce inside the host. However, one is born with a genetic disorder. They are caused by single, mutant alleles. In most genetic disorders, these alleles are recessive.
D 40. Explain how the processes of genetic mutation and natural selection are related to the evolution of species.
Population/ Gene Pools

D40. Natural Selection is a theory of how organisms evolve and change within their population. It can be broken down into five main parts:
1. There is a variation within populations caused by a genetic mutation.
2. Some variations are favorable.
3. More young are produced in each generation than can survive.
4. Those that survive and reproduce are those with the favorable variations.
5. Over enormous spans of time, small changes accumulate, and populations change.
Natural Selection
Watch 1:55-3:15

D 41. Explain how the current theory of evolution provides a scientific explanation for fossil records of ancient life forms.

Evolutionary Changes and Vestigial Structures:

Convergent evolution is the process whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.


Analogous: body parts that serve the same function in different species but they evolved independently rather than from the same embryological material or from the same structures in a common ancestor. An example of an analogous structure would be the wings on butterflies, bats, and birds.

Divergent evolution occurs when two or more biological characteristics have a common evolutionary origin but have diverged over evolutionary time.


Fossil records show that various species of organisms have similar fossil structure to current species due to the fact that they evolved according to their surroundings.

Homologous Structures: are characteristics which are shared by related species because they have been inherited in some way from a common ancestor. For example, the bones on the front fins of a whale are homologous to the bones in a human arm and both are homologous to the bones in a chimpanzee arm. The bones in all of these different body parts on different animals are basically the same bones, but their sizes are different and they serve slightly different functions in the animals where they are found.
Vestigial Structure: a structure that has little or no function and disappears over time in an organism, such as hipbones in whales and appendices in humans

D 42. Describe how structural and behavioral adaptations increase the chances for organisms to survive in their environments.

Every species has a unique set of adaptations that enables it to live in its environment. Some, like humans, starlings, and cheatgrass, have a wide tolerance to environmental constraints. Others, like Townsend's big-eared bats, three-toed woodpeckers, and the out-of-tune sticky tofieldia can survive only in the few niches where their unique habitat requirements are met. Most of Earth's biodiversity falls in the second category.
Over time, species adapt to changing environmental conditions
structurally and behaviorally. Small, light-colored leaves covered with fine hairs are a structural adaptation some desert plants have to conserve water. Being nocturnal is a behavioral adaptation many desert animals adopt for the same reason. Humans have succeeded in exploiting every habitat on Earth because the structural adaptations of our big brains and our hands enabled us to make the myriad behavioral adaptations necessary to live in so many places.
Some plants are extraordinarily tolerant of drought. They can withstand cell moisture levels that would be lethal for other plants. Sagebrush and bitterbrush are exceptional at extracting water from dry soils and living on very little moisture.
Plants can avoid drought with physical adaptations like the leaves of scorpionweed that funnel rain and dew toward its roots. Succulents like cacti collect water when it is abundant and retain it in their tissue. Rabbitbrush’s small, light-colored leaves reduce evaporation.
Plants escape drought by living in the few places where water is actually plentiful. Others, like the dwarf monkeyflower, carry out their entire life cycle during three moist weeks in the spring and survive as seeds during the rest of the year.

Grade: Adaptation and Why it is Neccessary (In Simpler Terms):

D 43. Describe the factors that affect the carrying capacity of the environment.

Carrying Capacity of an Environment: The environment’s ability to sustain life.

Factors that affect carrying capacity:
· Amount of food and water
· Availability of shelter
· Population density
For Humans
· Sanitation
· Medical Care
· Housing

D 44. Explain how change in population density is affected by emigration, immigration, birth rate and death rate, and relate these factors to the exponential growth of human populations.

Population density: a measurement of population per unit area or unit volume.
As people
emigrate (leave an area), that population density would decrease.
As people
immigrate (enter an area), that population density would increase.
birth rate increases, population density increase, and as birth rate decreases, population density decreases
death rate increases, population density decreases, and as death rate decreases, population density increases.

Grade: An explanation and directions on how to calculate population density:

D 45. Explain how technological advances have affected the size and growth rate of human populations throughout history.

D. 45**
Technological advances that have affected population growth
· Medicines (healthcare)
· Computers (research and communication)
· Housing/Standard of living (heat and air conditioning, toilets, stove)
· Schools (education = knowledge = college = professions = money = house = children)
· Cars + pollution + accidents = Death
· Factories + pollution
· Nuclear power