1. Inheritance and Adaptations
Chapter 7

2. Inheritance and Traits
Lesson 1
Inheritance and Traits

3. Inheritance Can you name more?
A trait is a distinguishing characteristic of an organism.
During reproduction, traits are passed down from one generation to the next, this is known as inheritance.
For every organism there is a range of inherited traits.
Hair color
Eye color
Petal color
Attached ear lobes
Can you name more?

4. Inheritance (copy entire slide)
Not all traits are inherited.
An acquired trait is a trait that an organism acquires or develops during his lifetime.
Loosing a limb (arm/leg)
Learning a trick/sport
Neat handwriting
Growing long hair
Can you name more?

5. Inheritance
Organisms pass traits to their offspring in one of the two ways:
Asexual reproduction – it produces offspring who are identical to the original; passing of traits by cell division and mitosis
Example: amoebas, bacteria, and some plants
Sexual reproduction – produces offspring that are similar but not identical to the parent or parents; requires DNA from both reproductive cells
Example: humans, most species

6. DNA & Genes DNA – (Deoxyribonucleic Acid) contains genes
DNA appears as a twisted zipper in the nucleus; when stretched out can be almost 2 meters long! It can fit into a cells nucleus since it is tightly coiled with proteins to form chromosomes.
DNA – (Deoxyribonucleic Acid) contains genes
Genes – a section of DNA that has genetic information for one trait
Genes carry instructions for traits.

7. Chromosomes
Chromosomes are found in the nucleus and carry long pieces of DNA.
The number of chromosomes differs depending on the species and in most species they come in pairs.
Humans have 23 pairs of chromosomes in each body cell.
Each pair contains one chromosome from the father and one from the mother.
Reproductive cells are known as the sperm and egg; each contains 23 single chromosomes. Within each chromosomes lies hundreds or thousands of genes.

8. Meiosis Much of this randomness is due to meiosis.
During meiosis, new sperm cells and egg cells form when the chromosomes in existing cells replicate and divide.
The number of chromosomes is reduced by half  23 chromosomes
One reproductive cell (with replicated chromosomes) will split into 4 separate cells, each containing a unique combination of genes.

9. Fertilization
Occurs when egg cell and sperm cell combine to form an offspring with a full set of paired chromosomes.
Resulting in unique offspring.
There are many potential gene arrangements when chromosomes combine in humans.
A mother and father could have billions of offspring and no two would be alike.

10. Combining genes
During reproduction an egg cell and a sperm cells each contribute one gene for a trait.
Each gene for a single trait is called an allele.
Traits are expressed in the offspring by chance.

11. Combining Genes
Dominant Allele – one whose trait shows up in an organism when an allele is present; represented by a capital letter
Recessive Allele – a trait that is hidden whenever a dominant allele is present; represented by a lowercase letter
Homozygous – an organism that has two identical alleles for a trait
Heterozygous – an organism that has two different alleles for a trait

12. Can you pick out the dominant alleles. … Recessive alleles
Can you pick out the dominant alleles? … Recessive alleles? … Homozygous? … Heterozygous?

13. Influencing Traits
Genotype – the GENetic makeup--an organisms complete set of genes; once inherited it remains unchanged.
Phenotype – the Physical appearance- how a trait appears or expressed

14. Punnet square
… is used to predict the possible outcomes of offspring.

15. Environmental factors
An organism’s environment can influence traits expressed by the genotype
Environmental Factors, such as physical and social factors, are not constant and can alter an organisms phenotype
These factors do not change an organism’s DNA or genotype
Light, nutrients, moisture, and temperature are physical factors that will affect an organism’s phenotype
An organism’s social group can also affect color, body structure, or behavior

16. Physical Factors Light is a physical factor.
Example: Plants need light. Plants that grow tall in full sunlight, might not grow as tall in low light.
Nutrients can also affect trait expression.
Examples:
Low levels of nitrogen or iron in the soil may turn a plant’s leaves yellow or cause them to fall off.
Flamingos are born white, but turn pink because of the food they eat (algae and crustaceans) are rich in red pigment.
Moisture and Temperature are also physical factors.

17. Social Factors
An organisms social group can also affect color, body structure, or behavior.
Examples:
Locusts are usually solitary individuals and are a green color. When locusts are in large groups they apply pressure on each others legs, causing them to change color to yellowish-brown and swarm.
Flamingos live in large social groups. A flock consisting of at least 20 is needed for breeding to occur in zoos. Adding more birds to a flock increases breeding success. In the wild these birds will live in flocks of 10,000.