SBI3UP - Evolution

L1: Biological change over time

Mutations

Changes in genetic sequence (DNA)

Effects of mutations

Can have immediate and direct effects on individuals, but can also influence future generations when those mutations are inherited

New or altered ___ arise when new ____ and ____ are produced by a _____

genes

alleles

genes

mutation

types of mutations effects

beneficial

harmful

neutral

Neutral Mutations

No immediate benefit or harm to the individual

Does not affect survival or reproduction.

Not selected by natural selection

Does not result in any selective advantage or disadvantage.

examples of neutral

hairline receding, webbed toes, etc.

Harmful Mutation

Reduces the organism's reproductive success and is therefore selected against.

Harmful mutations do not accumulate overtime (not selected for)

examples

SCA (sickle cell anemia)

cystic fibrosis

huntingtons disease

why do harmful mutations not accumulate

people with them die before reproducing

Beneficial Mutation

Increases the organism's reproductive success

Beneficial mutations are favoured by natural selection (BETTER ADAPTED TO ENVIRONMENT) and accumulate over time

Provide advantage - better chances of survival

examples of beneficial mutation

Sickle cell anemia carrier, lactose tolerance

Consequences of Mutations

Changes through mutations can have significant consequences:

Bacteria resistant to antibiotics

(less-resistant strains killed off, and resistant ones survive, making antibiotics less effective)

Insects resistant to pesticides

Influenza virus - changes all the time, enhancing its ability to spread

The Modern Evolutionary Synthesis

The modern theory of evolution takes into account all branches of biology

Evolution (described by modern evolutionary synthesis)

Biologists define evolution as changes in the gene pool of a species over time

Gene pool

consists of all of the alleles of all individuals that are currently present in a species or population

Individuals vary in _____ based on different _____ of _____ they _____

traits

combinations

alleles

inherit

Selective Breeding/

Artificial Selection of Traits

selective breeding is a part of artificial selection of traits

Occurs in captivity

Humans choose which animals or plants are bred (have certain desired trait(s))

Used to improve or modify particular traits

Can produce drastic changes in the traits

Produce new breeds or varieties of plants & animals

Artificial selection of traits/selective breeding: Domestication

the changing of members of a species to suit human needs through controlled captive breeding (artificial selection)

Ex. Dogs have descended from wolves, domesticated cow/pig/sheep/wheat/crops

Domestication of animals and plants is important, why?

provide humans with food supply

protection

selective breeding in plants

GEN 1 - breed desired traits: highest yield and largest fruit plants

GEN 2 - Repeat, breed best 2

GEN 3: best quality plant (best traits) made for human survival

Artificial Selection Procedure

1 Choose a useful species that can be bred in captivity

2 Breed a large number of individuals from one species.

3 Choose a trait from the population that would be useful.

4 Identify individuals that exhibit the trait most strongly.

5 Breed only these individuals to produce the next generation.

6 Repeat steps 4 and 5 over many generations.

afterward: when successful, the genetically modified individual is often massed produced by cloning

The Power of Artificial selection

Reduce genetic diversity within a population'

Some favoured traits can be linked to detrimental alleles

production of individuals that exhibit traits far beyond the original breeding population

e.g.

chihuahua; way smaller than wolf

Consequences of Artificial Selection

When a particular trait is selected for exclusively, often other traits become negatively affected.

e.g.

English bulldogs bred to have flat faces → many suffer from respiratory problems.

Often decreases genetic diversity

-makes the population less fit for environmental changes

Limitations of Artificial Selection

Cannot create traits that do not already exist in some form

Breeders can only work with traits that currently exist in the population

Or resort to genetic engineering technology to alter it

Mutations - new material to work with

Undesirable traits may accompany beneficial ones

no horns gene

polled-dominant

READ ACTIVITY BEFORE QUIZ

L2: The Evolution of an Idea

Evolution of an Idea

Philosophers, religious experts and others believed that the species that existed on the Earth were immutable - unable to change

All living things were created in their present form

mutable

able to change

immutable

unable to change

Georges-Louis Leclerc de Buffon contributions

examined animal body structures

Wondered about vestigial body parts - seemed to serve no purpose/marginally functioning.

Believed species had been created in a more perfect form but had changed over time.

vestigial

(of an organ or part of the body) degenerate, rudimentary, or atrophied, having become functionless in the course of evolution.

example of vestigial features

pigs:

pigs have extra toes that do not even reach the ground

have no purpose (vestigial)

result of evolution

the father of taxonomy

Carolus Linnaeus

Carl Linnaeus "the father of taxonomy" and Erasmus Darwin contributions

Proposed that life changed over time.

Erasmus Darwin (grandfather of Charles Darwin) even suggested that all life might have evolved from a single original source.

Had these ideas, but no explanation yet

Lamarck contributions

Lamarck proposed that evolutionary change resulted from two distinct principles

His 2 principles

Lamarck's First Principle: Use and disuse

Lamarck’s Second Principle: Inheritance of acquired characters

Lamarck's First Principle:

Use and Disuse

Structures an individual used became larger and stronger

Structures that were not used became smaller and weaker.

Lamarck`s Second Principle:

Inheritance of Acquired Characters

Individuals could pass on characteristics they had acquired during their lives.

2nd principle example

Believed that if an adult giraffe stretched its neck during its lifetime, then its offspring would be born with slightly longer necks.

Flaws of Lamarck's 1st and 2nd Principle

1st:

Although organisms can acquire many characteristics during their lives, many features do not change in response to use, and

2st:

features that do change are not normally heritable.

flaws examples

1st principle: Vision does not improve the more you use your eyes.

2nd principle: possible to stretch your neck slightly, but this will not alter your DNA , your children will not be born with longer necks.

Lamarck proposed the following:

Although his theory was flawed, Lamarck made significant contributions to our understanding of evolution

-All species evolve over time.

-A species evolves in response to its environment and becomes better adapted to that environment.

-Changes are passed on from generation to generation.

-Base for the theory of evolution

Patterns of Change / evolution evidence: how are fossils formed

Fossils are formed when the remains of a buried organism are gradually replaced by mineral deposits.

fossils

Fossils are preserved ancient remains, hard impressions in solid rocks (remains of dead organisms).

fossilization steps

1. Remains of a buried organism are gradually replaced by mineral deposits

2 . After an organism dies, the body usually decomposes.

3.If it sinks to the bottom of a body of water and is quickly buried by sediments, the resulting lack of oxygen can prevent decomposition.

4.As sediments accumulate, the body becomes compressed, and very gradually chemical changes occur that result in the body being mineralized.

Conditions for Fossil Formation:

-Low oxygen (when oxygen is present it causes things to decompose quickly)

-Hard body parts more likely to be preserved (shells, bones, teeth)

-Fossils of aquatic/marine animals more common than land animals

-Can also be preserved in amber, volcanic ash, ice formations

Reading the fossil record revealed that fossils are:

-Unusual and unknown organisms (few fossils of known organisms)

-No fossils for most living species

-Buried deep in rock formations-more than a km below earth's surface

-Found in unexpected locations (sea life in mountains and deserts)

Paleontology

the scientific investigation of prehistoric life through the study of fossils

paleontology: fossils at the bottom are the ____

oldest

Georges Cuvier contributions

Simple organisms are found in all depths of fossil deposits

Complex organisms are found near the top - younger rocks

Organisms near the top are more likely to resemble living species

Rock layer contain fossils of many species that do not occur in layers above or below them

Which theory did Cuvier create

Catastrophism

Catastrophism theory

-species themselves did not change

-global catastrophes such as floods caused widespread extinction of species

-extinct species fossilized, and replaced by a newly created set of species.

how did the catastrophism theory contradict his findings

catastrophism contradicts more complex fossils at the top, since if species did not change how is that possible

Catastrophism theory criticism/flaw

-Cuvier’s theory accounted for the different groups of species in each layer but did not adequately account for why each layer included progressively more complex forms

Uniformitarianism theory

-earth has been changed by the same processes in the past that are occuring in the present

-Geological change is slow and gradual/uniform (rather than fast and catastrophic).

-Earth is extremely old and life had had a very long time to undergo evolutionary change.

opposite/contradicting theories

catastrophism vs uniformitarianism

proposed that evolutionary change resulted from two distinct principles

Lamarck

Theory of catastrophism

Georges Cuvier

Uniformitarianism theory

Sir Charles Lyell

Uniformitarianism vs catastrophism

Catastrophism:

species didnt change

rapid events (flash floods, etc.) causing mass death

does not show evolution

proves why different species are found in different layers, but does not show why it becomes more complex

Uniformitarianism:

species do change

gradual changes to earth through slow processes

aids in the theory of evolution: environment changed slowly and so did species

proves why different species are found in different layers and also shows why it becomes more complex

how does catastrophism contradict and also support culviers claims about fossils and evolution

could show why there are different species on different layers: due to mass extinction with species replaced with other species

did not show how it becomes more complex as you go higher: says that all species die, but how do they become more complex?

how uniformitarianism supports some of culviers claims

says that earth changes slowly with eternal processes, species changes with it, : PROVING why it becomes more complex

some gradual changes can cause extinction

L3: Evidence for evolution

Evolution process steps

1 genetic information is passed down

2 genetic information is mutated

3 species are changing over time

Sources of Evidence for Evolution

biogeography

fossil record

embryology

anatomy

DNA

Biogeography

The study of past and present geographical distribution of organisms

Galapagos islands and other remote islands have:

-Unusual assortment of species (strange combinations, endangered)

-Unusual examples of animal behaviour (species are fearless – willingly interact with humans)

_____ related species are usually found in ___ that are geographically ___ to each other

closely, areas, close

Modern Paleontology

Last 100 years, important fossil discoveries

Distribution of fossils

Plate Tectonics

- the scientific theory that describes the large-scale movements and features of the earth's crust

What does plate tectonics/continental drift explain about fossils

Explains why fossils of the same species can be found on different continents

Darwin’s Hypotheses Regarding Remote Islands

-Remote oceanic islands became populated by species that arrived by water or air

-After the species became established, they evolved into new species over time

-Isolated species have a resemblance to species on the nearest continental land mass

darwin observation #1 about the islands and hypothesis

many species of birds, reptiles, plants, insects

hypo: only these types of organisms are able to reach remote islands by crossing large expanses of ocean

ob #2, hypo

no native amphibians and very few land mammals

amphibians and land mammals cannot travel across oceans

ob #3, hypo

many unique species found nowhere on earth

over time, ancestral species have evolved into new geographically isolated species

ob #4, hypo

unique species most closely resemble to species on the nearest continental land mass

unique species are descendants from ancestral species on nearest continental land mass and will exhibit some similarities

Testing Darwin’s Hypotheses , use Hawaii as an example

If correct, they would apply to similar situations

Test Case - Hawaiian Islands:

Native species here support Darwin’s Hypotheses

No native amphibians or mammals (except bats and sea lions)

Unique plants, bird, and insects

Only reptiles are marine species

When testing a hypothesis,

it is important to consider alternative explanations

alternatives to darwins hypotheses

Maybe remote islands lack certain organisms because these species are not able to live in such settings

Tested when non-native species are introduced to islands

Introduced Species to remote islands

Thrived in new environment

But had devastating impacts on many native species

Ex. Rats, dogs, and pigs eating baby eggs on the ground

Many species in Hawaii have been extinct after the arrival of Europeans in 1778

Therefore, mammals and amphibians ___ survive on remote islands. So we ____ accept the alternative hypothesis..

cant

cannot

Homologous Features

Similar structural elements and origins, but with different functions

example of homologous features

Example: Bat wing and human arm

All _______ have an almost ________ number and arrangement of bones

mammals

identical

Why were the bones in all mammals so similar in number and arrangement?

-Homologous features could be explained by evolution

-Closely related species share common ancestors, developmental processes, and patterns

-Degree of similarity between homologous genes provides evidence for degree of relatedness between species

Homologous Features

- Embryos

In early developmental stages - embryos of all vertebrates possess a short bony tail

Human embryos also have gill slits even though we do not have gills by the time we are born

homologous features characteristics

similar structure

different function

Analogous Features

Features that perform similar functions but have different origins and structure

Same function but different in structure and only distantly related

Example of analagous features

Example: eyes and wings of insects vs. the eyes and wings of birds

Vestigial Features:

Features that no longer serve the function they do in similar species

Non-functioning or only marginally functioning structure

Vestigial Features examples

Ex. Human appendix, wisdom teeth

Pseudogenes

Pseudogenes - Genes that have undergone

mutations and no longer serve a useful purpose

Pseudogenes example

Dolphins

No need for a sense of smell, yet have the same 1000 genes

for smell that mammals do

200 functional. 800 pseudogenes

Mutations to make these genes dysfunctional are neutral

Competition with Populations

Anatomical features, biogeography, and the fossil record provided Darwin with evidence for evolution

Could nature favour certain individuals in a population just like human breeders?

Thomas Malthus theory

Competition with Populations

Competition with Populations theory description

-Showed that all populations were limited in size by their environment (in particular their food supply)

-Populations cannot grow indefinitely

-Many species produce large numbers of offspring but not all survive

-Competition for survival between members of the same species

Competition with populations cont.

Competition for survival between members of the same species is intense - Vying for the same resources

Environment favouring certain individuals

Assessing the Evidence (Darwin)

His evidence supported evolution, but he knew it would be controversial and conflict with religious beliefs

Darwin believed species had evolved, and that his theory could explain how