Chapter 2 Section 1 – discussed the effect of the

environment on the phenotype of individuals –

light, population ratio, type of soil,

temperature…)

Chapter 2 Section 2: how traits are passed from

the parents to the offspring

Chapter 2 Section 3:

Environmental impact on a whole population

over time

( or: the effect of the environment on the

inherited traits of a species as a whole, not only

individuals)

We will study Evolution

What is Evolution?

It is the change in the genetics of a

species over time

( if the genotype changes, also the

phenotype will change)

Old ideas about Evolution

Beginning of the 1800’s :

all known species were created at the same

time and remained unchanged throughout

history.

Creationism – is the name of the theory

that explains that all creatures were

created by God.

Old ideas about Evolution

There are 2 main initial Evolution

Theories

Lamarck’s theory

Darwin’s theory

Lamarckism - 1809 Acquired traits could be passed onto the offspring.

Ex: The ancestors of giraffes had only short necks. Giraffes

had to compete to obtain food, had stretch their necks to

get food and passed this trait to the offspring.

WHY WAS LAMARCK WRONG????????????????????????

Lamarck was wrong because inherited

traits are not in an organism’s genotype,

so cannot be passed to the offspring!!!!!!!

Darwin – 1850’s

explained Evolution through his Theory of

Natural Selection

handout page 190

Evolution through Natural Selection – Giraffe’s neck

according to Darwin

Initially, there were giraffes with long neck and

short neck ( important)

The giraffes with long neck had an advantage.

They could feed themselves better than the

ones with the short neck

The giraffe’s with long neck survived better

and reproduced more, generating more

offspring

With time, all giraffes had long necks because

the short neck ones could not survive and went

extinct.

Natural Selection

also called Survival of the Fittest

This theory explains that organisms with

traits best suited to the environment

they inhabit, are more likely to survive

and reproduce, generating more

offspring.

** These traits, that give “survival

advantage” to certain individuals, are

called FAVORABLE

**Modern Theory: Neo-Darwinism

Neo - Darwinism adds knowledge of genetic

inheritance to the Theory of Natural Selection.

Today we know that the gene pool of a population

can change due to mutations and sexual

reproduction.

These changes will pass from parent to offspring

and the whole population will change over time.

Imp: The ultimate goal of any organism is to reproduce

and pass the genes to the offspring.

Charles Darwin

The Theory Of Natural Selection

https://www.youtube.com/watch?v=vnktXHBvE8s

Darwin’s Theory of Natural Selection –

Important principles that led to this

theory:

mentioned in the video and written in the

handout page 191

Darwin’s Theory of Natural Selection -

Important principles that led to this

theory: ( video and also in the handout

page 191) Number 1:

Organisms produce more offspring

than the amount that can or will

survive

Darwin’s Theory of Natural Selection -

Important conclusions that led to this

theory: (see handout page 191)

Number 2:

Individuals within a population have

different traits, so there is variation of

traits among individuals of a species

(There were giraffes with long neck and

short neck)

Darwin’s Theory of Natural Selection

Number 3:

The different traits are passed from

parent to offspring

(If there are more giraffes with long

neck surviving, the percentage of this

trait in the population will be higher)

Darwin’s Theory of Natural Selection

Number 4:

Individuals with favorable traits are

more successful at surviving and

reproducing

Long neck is a trait that represents an

advantage and will help giraffes

survive and reproduce

Darwin’s Theory of Natural Selection

Over time, this process can result in populations

that are specialized to live in certain

environments

These populations have traits that will help

them survive in the environment better than

other populations without the trait

this trait will become DOMINANT in the

population

This process can lead to the appearance of new

species

Concept Review:

Underline in your printout the following

terms:

- Species

- Evolution

- Natural Selection

- Variation

- Adaptation

Adaptation – any trait (structural or behavioral) that helps an organism survive and reproduce in a particular environment

Variation – inherited trait that makes an individual different from other members of the same species

Variations can be a result of sexual reproduction or mutations.

Read handout page 191

Vocabulary:

**Speciation - is the process of forming a new

species through evolution

Species – a group of organisms with similar

characteristics that can reproduce and

generate fertile offspring

Speciation can happen due to:

Geographic Isolation and Changes in the

environment

read printout page 192

Speciation due to changes in the

environment

Speciation can happen if there is a change in

the environment. Organisms better equipped

to the new conditions will survive, others will

disappear.

Survivors will reproduce, increasing the

presence of the favorable trait in the

population and can also suffer mutations

generating new species, over time

Adaptive Radiation:

During his trip to South America, Darwin observed a process called Adaptive Radiation, due to geographical isolation

**Adaptive Radiation is the production of

several species from one ancestral species

• Case of the finches in the Galapagos Islands –

• Read handout page 190

The ancestral finch migrated from the mainland to nearby

islands and had to adapt to survive.

The type of beak that helped the bird survive in a certain

area, is the trait that will remain in the population.

Ancestral

finch

Section 3 in the textbook:

Environmental Impact over Time

Factors in the environment that will affect

entire populations over time

The factors can be: Non-living and Living

*Nonliving = ABIOTIC

*Amount of water

*Temperature

*Food availability

*Air pollution

*Type of soil for plants

*Light

*Availability of space to live

*Living = BIOTIC

*The presence of predators

*The presence of other species that will

compete for the space, food, water

*For Plants – the presence of species

that will compete for light

**Mutation

• Is a change in the DNA resulting in new alleles and in variations in traits

• A mutation can be the result of exposure to chemicals, radiation, or mistakes during the DNA replication

• A mutation can be good, bad or neutral for the population

**Mutation

• The variations that results in favorable

traits for the species tend to remain in the population and be passed to other generations.

• The variations that do not help an organism survive and reproduce tend to disappear from the population.

**Selective Breeding – Artificial process of

“natural” selection

Selective breeding is the process by which humans

breed animals and plants to develop an offspring

that will possess desirable traits

1) Breeders observe which traits are desirable in a

certain population

2) Breeders cross animals or plants that show the

desirable traits to obtain offspring that have that

certain trait

EX: Animals – faster or stronger

Plants – more resistant to illnesses, parasites or

cold….

**Extinction of Species

• Extinction occurs when the last individual of a species dies.

Reasons:

1)**Overharvesting, Hunting

(reducing natural stocks)

2)Pollution and habitat destruction

3)Introduction of new species

(such as new predators and food competitors that will

affect the ecological balance to the community

of a certain area)

** Diversity - is the variability of traits among

all living organisms

** Environment - Everything that surrounds

an organism and can affect its development

and survival.

Physical environment – non living - abiotic

Biological environment – living – biotic

Examples can be found in pages 49 and 50 of

the textbook