ged science: life science part 2 organization of life, heredity and evolution

GED Science: Life Science Part 2

Organization of Life, Heredity and Evolution

The Cell

• The smallest unit of living things• All living things are made of cells• Cells come from cells• All parts of the body are made of specialized

cells

Animal Cell

Cell Structure

• All cells have a membrane to regulate what can pass into it

• Organs inside cells with different tasks are called organelles

• Cells vary based on their function/body system

• Cells also contain chromosomes that contain information about the cell’s genetic makeup

Cell Metabolism

• How nutrients are turned into energy• Carbohydrates are transformed into energy• Enzymes are used as catalysts (assist the

process)• Energy is used to produce proteins or carry

out functions

Mitosis

• Mitosis is how cells reproduce

• Chromosomes double into two identical sets

• Cell divides into two daughter cells

Meiosis

• Meiosis is when cells divide leaving two cells with half the number of chromosomes

• Meiosis is used for cells in the reproductive systems of organisms with sexual reproduction

Heredity

• DNA is the code on the chromosomes for traits

• Cells created by meiosis from both parents form a zygote

• Zygote has the full number of chromosomes for the species

Alleles

• Alleles are different versions of a gene• Alleles can be recessive or dominant• If an organism contains dominant and

recessive alleles, the dominant allele is shown• Punnett squares calculate probability of an

allele being shown

Punnett Squares

B b

B BB Bb

b Bb bb

Punnett Square for chicken feather color:B allele- Blue feathers (dominant)b allele- White feathers (recessive)Both parents are Bb (blue)

Genotypes and Phenotypes

• Genotypes- the genetic makeup of an organism (ie Bb)

• Phenotype- The observable trait (ie blue feathers)

Mutation

• When DNA is damaged or error is made in replication of chromosomes, mutations can occur

• Mutations can result in traits that neither parent has

Adaptation

• Traits may change over time to adapt to environment

• Darwin’s finches: finches in the Galapogos Islands beaks adapt to local plants

Selection

• Traits become more or less common in a species

• Key component of evolution• Natural Selection: organisms with desirable

traits for the environment more likely to reproduce

• Artificial Selection: Selective breeding of organism

Cladograms

• Diagram showing relationship between organisms

• Similar organisms are grouped on branches

• Evolutionary trees are similar to cladograms and show ancestors of species

Selection pressure

• The environment can put pressure on a species to change

• Drug resistance: bacteria can evolve to become resistant to antibiotic drugs

Photo: Joseph Berger

Speciation

• Speciation is the process by which new species arise

• Apple Maggot Fly: New species appeared after apples were introduced to North America