Savvas Realize Science Topic 3 Lesson 1

Asexual Reproduction

Asexual reproduction is a reproductive process that involves only one parent and produces offspring that are genetically identical to the parent.

• One for of asexual reproduction is fragmentation, where a new organism forms from a piece of the original (ex: starfish).

• Another method of asexual reproduction is budding, where a new animals grows out from the parent until it fully matures and breaks off (ex: sponges).

Sexual Reproduction

• In sexual reproduction, two parents combine their genetic material to produce a new organism that differs from the parents. It involves a sperm cell (father) and egg cell (mother) joining to form a new cell in a process called fertilization. Each parent gives half their chromosomes so the offspring has a full set.

Traits and Genes

• A specific characteristic that an organism passes to its offspring through its genes is called a trait. A gene is a sequence of DNA that determines a trait passed from parent to offspring.

• Differences in offspring are known as variations.

Comparing Types of Reproduction

• Benefits of asexual reproduction are that organisms don't need to find a mate, and can reproduce quickly. However, all offspring have exactly the same genetic makeup, which can be a problem if the environment changes.

• Benefits of sexual reproduction are that offspring have more genetic variation (increasing their chances of survival if the environment changes). However, the organism needs to find a mate.

Inherited Traits

• Inheritance is the process in which offspring receive traits from their parents. Genes are located on chromosomes and describe the factors that control a trait. Each trait has a gene from the mother, and a gene from the father (which can be the same or different).

Alleles

• An allele is a different form of the same gene. One allele is received from each parent and the combination of alleles determines the offspring's traits.

• If an offspring inherits a dominant allele from either parent, that trait will always show up. An offspring has to receive two recessive alleles from both parents for the trait to show up.

Incomplete Dominance & Codominance

• Sometimes, intermediate forms of a dominant trait appear. This creates a mixture/blending of the recessive and dominant traits known as incomplete dominance (ex: pink rose).

• Codominance is when two alleles are expressed. (ex: spotted flowers, AB blood)

Multiple Alleles

• Every offspring has two alleles for a certain trait (one from the mother and one from the father). However, some traits have multiple alleles, such as blood type (A + B are codominant, O is recessive).

Polygenic Inheritance

• In polygenetic inheritance, different genes are expressed to produce a trait (ex: human height, skin color; there is a range).

Acquired Traits

• Traits that are learned are called acquired traits. The combination of inherited and acquired traits helps an organism to survive

Environmental Traits

• Gene expression determines how traits appear. The environment can lead to changes in gene expression. (ex: chemicals in tobacco or exposure to the sun's UV rays) In order to pass on genes that have been affected by the environment, the change must occur in the sperm or egg cells.