CHAPTER 3REPRODUCTION Lesson 1 What is Asexual Reproduction? Heredity – the passing of traits from parents to their offspring Three factors influence or affect an organism’s characteristics: 1.) heredity (inherited traits)- all organisms inherit traits 2.) environment – organisms require nutrients, clean water, and other needs to reach the potential of your inherited traits. Ex.) If you keep a plant out of the sun and don’t water it then it can’t grow to its potential. 3.) learned traits – can not be passed from parent to offspring

Asexual Reproduction: offspring come from a single parent and offspring has identical DNA as that parent. Passing traits from parent to offspring is needed for the species to survive. 4 Kinds of Asexual Reproduction: 1.) Fission: fastest way of reproduction, one parent cell splits and divides into two equal, identical offspring (the parent no longer exists) 2.) Budding: a cell in the parent produces and grows a small version of it ex)yeast, some plants, hydra(protists)

3.) Spores: one reproductive cell with a complete set of DNA ex.) mold, ferns 4.) Fragmentation: forming offspring from body parts ex) some plants, starfish

Lesson 2 How Are Traits Passed On? Structure of DNA Chromosomes(in the nucleus) contain instructions for a cell’s activities. Chromosomes are tightly coiled structures made of proteins and DNA. Chromosomes are twisted or coiled so they fit in the nucleus. Even under a microscope you can only see chromosomes during cell division.

DNA is passed from a parent cell to its offspring. DNA are ‘twisted ladders’ made of millions of rungs. DNA rungs are made up of four base chemicals. Base A pairs with Base T and Base C pairs with Base G.

Gene – is a series of base pairs (sets of DNA that work together to control a trait)

Copying DNA DNA of all living things is made up of the same 4 base pairs. The arrangement of the base pairs are what make each living thing unique. During mitosis, chromosomes ‘unzip’, bases come apart and pair up with a copy of each base pair.

A Mutation is when an error occurs during the copying of DNA. The mutation changes the gene’s instructions and can be passed on to offspring. The Human Genome Project: scientists mapped all 30,000 genes that make up the 46 human chromosomes.

Lesson 3 Sexual Reproduction Reproduction by Two Parents Offspring will receive half its chromosomes (DNA) from each parent. Ex)a fox has 64 chromosomes(32 chromosomes come from each parent) Male sex cell (sperm) has half the male parent’s DNA and it combines with the female sex cell (egg) which has half the female parent’s DNA. Fertilization is when the sperm cell joins with the egg cell. The fertilized egg that forms is called a ZYGOTE. This is the first cell that will then undergo mitosis. (half from sperm + half from egg= 1 whole set of DNA)

Meiosis: only sex cells split again after mitosis without copying its DNA. Steps: 1. sex cells go through mitosis and form 2 equal identical cells 2. the chromosomes in each cell split again without copying DNA 3. So there are 4 cells now with only half the DNA in each (each human sperm cell has only 23 chromosomes)

Fertilization in Flowering Plants: Inside a pollen grain is the sperm cell. The sperm cell needs to land on the pistil of a flower where the egg cell is.

Fertilization in Animals: Internal Fertilization takes place inside the female body. External Fertilization takes place outside the female body. Most animals that live in or near water reproduce externally. They release sex cells into the water and the sperm and egg cells unite there. External fertilization usually produces many sex cells because most will not unite while floating around in the water.

Comparing Sexual and Asexual Reproduction AsexualSexual One parent cellNeeds two parent cells to join Happens quicklySlower, longer process Takes less energyTakes more energy DNA is identical to parentDNA is unique and get ½ from each parent Identical offspring react the same to environmental changes Unique offspring may react differently to environmental changes

Lesson 4 How do genes determine traits? Dominant and Recessive Traits Offspring get 2 genes for every trait (one from each parent cell) Dominant traits are stronger traits that can hide the effect of others Recessive traits are weaker traits that are hidden by the dominant ones When an offspring has two of the same genes it is PUREBRED for that trait. When an offspring has one dominant gene and one recessive gene for a trait it is HYBRID. The dominant gene will show.

When a purebred dominant (red) parent has offspring with a purebred recessive (blue) parent, ALL offspring will be hybrid but will only show the dominant gene for red. When a hybrid (purple) parent has offspring with another hybrid (purple) parent, 1of4 will be purebred dominant purple, 2of4 will be hybrid but show purple, 1of4 will be purebred recessive white.

When a purebred recessive (green) parent has offspring with a hybrid (yellow) parent, 2of4 offspring will be hybrid and show the dominant yellow gene, 2of4 offspring will be purebred recessive and show the recessive green gene.

Sharing Dominance: in some cases 2 different genes have the same strength so neither of them is dominant over the other. When this is true, the genes will either both show or they will blend. bw b b wwww Since neither black or white is dominant, all offspring will have feathers of both colors. pw p p wwww Since neither purple or white is dominant, all offspring will be a blended color of pink.

Choosing Traits Selective Breeding: selects members of a species with desired traits to reproduce. This increases the chances offspring have those traits. Farmers and others use this to help produce crops with more food per plant or cows that produce more milk, etc.