Lab 2A--Life on Earth

Geology 1402

Chapters 3 & 7 in the textbook

1

A comment

• Many people including professional

scientist are skeptical of evolution or

outright reject it.

• I am not attempting to change your mind if

you are in that group.

• I am attempting to explain an idea that is

widely accepted by the scientific

community and is supported by extensive

evidence. 2

Evolution

• Broad definition: Change

• Organic evolution: Change in life forms

3

Organic Evolution

• How life has changed through time.

• How all life is interrelated through ancestry.

• Fossils: tangible record of changes in species

4

Linnaean Classification Scheme

• System for classifying (grouping)

organisms---usually by form

• Grouped by

– shared similar characteristics, that is to say,

– they have the same forms and look very

similar.

5

Why classify organisms?

• Avoid complete chaos

• Determine which have a common ancestor

-or-

• Who is related to whom

6

Caution

• Not all similarities mean a close ancestral

relationship

• Often similarities come from adapting to a

similar environment

7

Linnaean Classification Scheme

• DNA confirms relationships—has changed

some old ideas

• We find relationships with ancestors by

looking at the number of differences in

amino acid sequences which make up

DNA

8

Classification of Life (Fossils & Living Groups)

9 Source: http://www.windows2universe.org/earth/Life/classification_intro.html

Kingdom Fungi Kingdom Animalia Kingdom Plantae

Kingdom Protista

Single-

celled

organisms

Classification of Life (Fossils & Living Groups)

• Domain: Archaea—prokaryotes (bacteria)

• Domain: Eubacteria—prokaryotes (bacteria)

• Domain: Eukaryota--eukaryotes

– Kingdom Protista

– Kingdom Fungi

– Kingdom Animalia

– Kingdom Plantae

10

Lab book page 25— is out of date.

Monera was split into Archaea and Eubacteria.

Linnaean Classification

• Kingdom

• Phylum – Subphylum

• Class

• Order

• Family

• Genus

• Species

11

Lamarck—An Idea Rejected

• Inheritance of acquired

characteristics

• Organisms adapt—a

giraffe stretches neck to

reach high leaves

• Giraffe can pass the longer

neck to young

• No—It doesn’t happen

this way.

12

Evolution

13

Evolution

• Idea evolved slowly

• Many people before Darwin suggested

evolution

14

Darwin had read

Thomas Malthus • Malthus published: Essay on the Principle

of Population (1798)

• A key idea: “…favourable variations would

tend to be preserved, and unfavourable

ones to be destroyed.”

• Survival of the fittest.

15

Evolution

• Darwin on the H.M.S. Beagle (1831-1836)

– Observed bird populations on isolated islands

– Recognized different species but closely

related species (finches)

– Recognized the influence of environment on

differing species.

– Published On the Origin of Species (1859)

16

Evolution

• Basic idea: Species descended from prior

species

• Debated and accepted within a decade.

Very remarkable accomplishment.

• Controversy came when humans were

included in the theory

17

Note:

• Darwin never said:

Humans descended from monkeys.

• Darwin said:

Apes and humans have a common

ancestor. 18

Natural Selection

• “survival of the fittest”—the most suitable

for the environment (not the strongest!)

• This applies to individuals and to species

• Variations

– Some individuals able to survive better and

reproduce more abundantly

– Traits (forms) dominated

19

Keys to Natural Selection

• Variation within a population among

individuals.

• The variation must be inheritable.

• Differences in reproductive success based

upon those differences.

20

Artificial Selection

• Humans decide which

individual will breed with

which.

• Examples:

– Dog breeding

– Race horse breeding

– Cattle breeding

– Turkey breeding

21

What are the two things that

every living thing does? Eat Reproduce

22

What are the two things that

every living thing does?

• Eat & reproduce

• Pass on your traits:

– Eat better than your competition (survive)

– Reproduce more

23

Changes • Changes in organisms or populations are

often due to changes in the environment.

• The ones that survive are those that can

adapt and tolerate the environmental

changes.

• The successful trait must already be

available in the gene pool. (Discuss)

24

Genes, DNA & RNA

25

Genetics

• Gregor Mendel

– Published in 1865

– Unknown to Darwin

– Experimented with peas

– Demonstrated that traits from

each parent were inherited by

offspring

– Traits passed by genes

1822-1884

Austria-Hungary

26

Genes

• Genes are paired—one set from each parent

– Note: Sexual reproduction produces more variation than asexual reproduction.

• Genes do not mix (Key point!)

– Some are dominant and obvious

– Others are recessive and hidden

• Passing of genes produces variation in a population

27

DNA: deoxyribonucleic acid

• Genes are sections on the DNA.

• Allele: part of the gene that passes on the

trait to offspring.

• DNA molecules: basic hereditary units

• DNA: information for making proteins out

of amino acids

• Proteins make cells

28

DNA

• Each nucleotide

contains one of the

following:

– Adenine A

– Thymine T

– Cytosine C

– Guanine G

• These nucleotides

determine the

characteristics of an

organism 29

Mutations—How Change Happens

• Alterations in DNA

• Genes can move from one part of the DNA

to another

• Amino acids are substituted for others: the

code changes

30

What can cause mutations?

• Radiation (even ultraviolet radiation)

• Cosmic rays and gamma rays

• Chemicals

• Random changes in the genetic code

31

Are mutations good or bad?

• Comments from class.

• Discussion

• What do we call bad mutations in

humans?

• Bad—”birth defects”

• Good—helpful traits

• Neutral—makes no difference

• The call—How well does the organism

adapt to the environment?

32

RNA—Two Types

• DNA—inside the cell

• RNA—Passes through the cell wall

– mRNA—Messenger RNA: Carries message

from DNA to site where proteins are formed

(outside the cell)

33

RNA—Two Types

• DNA—inside the cell

• RNA—outside the cell

– tRNA—Transfer RNA: Ferries amino acids to

sites where they are assembled into proteins

(outside the cell)

34

Speciation

• The development of new species

• A change in the gene pool

• Isolated populations diverge, that is,

change and eventually cannot interbreed

• Now have a new species

35

What is a species?

• Species—

– Group of organisms

– Similar structure, function and development

– Able to produce fertile offspring (in nature)

• Examples of non-species:

– Mule (female horse and male donkey)

– Liger (tiger and lion—only happens in zoos)

36

Patterns of Evolution

37

Patterns of Evolution

• Divergent evolution

– A single species evolves into two distinct species,

each with distinctive traits

• Adaptive radiation

– Many new species evolving different traits to live in

different environments

• Convergent evolution

– Unrelated species exhibit similar adaptations when

they inhabit similar environments (wings: birds and

bats)

38

Divergent Evolution in Plants

All had a common ancestor

39

Adaptive Radiation

Bills Adapt

40

Convergent Evolution

41

Vestigial Structures

(Remaining structures)

42

How fast is evolutionary change?

• Phyletic gradualism

– Small changes over a long period of time

• Punctuated equilibrium

– Very distinct changes over a very short period

of time with little change in between these

“bursts”

• (draw diagram)

43

Comparison

How

quickly

does

change

happen?

44

Organization of Life

• Old way: Based upon observable traits

that arise from genetic processes.

• Now: A clade—a group of organisms that

share a common ancestor based upon

DNA analysis, not just observable forms.

45

Clade

• A clade—a group of

organisms that share

a common ancestor

based upon DNA

analysis, not just

observable forms.

46

Clade

Based upon DNA

similarity

47

Clade

Different species within

a category must have a

common ancestor

48

Clade

A clade—a group of

organisms that share a

common ancestor

based upon DNA

analysis, not just

observable forms.

49

Clade

50

Review of Classification of Life (Fossils & Living Groups)

• Domain: Archaea

• Domain: Eubacteria

• Domain: Eukaryota

– Kingdom Protista

– Kingdom Fungi

– Kingdom Animalia

– Kingdom Plantae

51

Any questions?

Please do lab two & the supplement.

Omit all questions in the lab book

that have a table to fill in.

52