Gr 11 Bio - Evolution

Malthas

* He wrote an essay on the principle of population
* the factors that limited population growth leads to competition for food.
* more offspring are produced than can survive
* bigger population = fewer resources

Wallace

* struggle of existence
* inferiors killed off and superior would survive (fittest survive)
* natural selection of inherited traits leads to new species

lyell

* geologist
* earth is much older than 8,000 years because of the sediments that came from the erosion of mountains
* small changes over time

E. Darwin

* different species come from common ancestor
* “E conchis omnia” : everything comes from shells
* acquire new traits and pass down improvements

Lamarck

* traits could be acquired by waning or needing them then they would be passed down
* “inheritance of acquired traits”
* species could change in response to environment

C. Darwin

* theory of Natural Selection
* the endless variation that will flourish or fade away (disease, hunger, predation, climate etc)

Fossil record

Fossil records show evolution because we can seen how species have changed through time since their remains have been preserved in layers of rock. Sometimes there’s “holes” in the fossil record which means there’s a missing like between two species.

Analogous Structures

Two unrelated structures with the same purpose that’s often related to convergent evolution.

Vestigial Structures

Body parts that have been reduced or are incompletely developed. They have little to no function but likely were once a key part of an ancient ancestor.

Homologous Structures

Similar structures that serve different purposes, often related to divergent evolution.

Biography

It’s the study of the distribution of life forms over geographical areas. From this we can see patterns as a result of tectonic plates and evolution. Fossil records show were each species once lived.

DNA Similarities

The more closely related species are, the more common their DNA is. We can use the sequence of amino acids in proteins and nucleotides sequences of DNA to see differences and similarities.

Artificial Selection (Evidence)

It’s a form of selective breeding where humans select desirable traits that suit our needs.

Ring Species

When a specie is separated by a large geographical barrier, it can cause new species to form because of the different environments. They take different evolutionary paths and are unable to interbreed when reunited.

Comparative Embryology

Study of embryos to identify similarities and differences between species during their development. We can see that they all look very similar early on in life.

Hox Genes

All vertebrates and some invertebrates have a similar set of genes. They are regulatory genes help to lay out basic body forms during development and much of the complexity of multicellular body parts began with one gene replication.

Resistence

Humans have unintentionally selected for drug resistant bacteria through the overuse of antibiotics, drug-resistant bacteria can grow and spread their resistance to others. This is a form of microevolution and is called a “biological arms race” because we need to develop stronger antibiotics to combat stronger bacteria.

Natural Selection

Random variation in individuals are selected by nature in a non-random way.

Selective Pressures

Result of abiotic or biotic factors that put pressure on a populaion.

Only source of new allele:

Mutations

What does variation within a species create?

A range of successful or unsuccessful genes.

Adaptation

Process that helps an organism survive and reproduce in a particular environment.

Behavioural Adaptation

Change affecting how an organism naturally or normally behaves. It can be identified by stimulus response. (reaction to change)

Physiological Adaptation

Involving a physical change that can’t be seen in their appearance

Structural Adaptation

Involves a visible, physical cahnge.

What does the Hardy-Weinberg equation do?

It quantifies evolution by measuring the frequency of alleles in a population to see if a population is in equilibrium.

5 Hardy-Weinberg Principles

* Population is Large
* Equal/random Mating Opportunities
* No Mutations
* No Migration
* No Natural Selection

Genetic Drift

Breaks “Population is Large” rule because in a small population, chance plays a higher role. It is change in genetic makeup of a population resulting from chance. It leads to the fixation of alleles, reduces genetic diversity and exaggerates differences by removing variation.

Bottleneck Effect

Form of genetic drift where something occurs and wipes out part of the population. The frequencies of the new population are different from those of the old. They do NOT move geographically.

Founder Effect

Form of genetic drift where part of a population MIGRATES. The frequencies of the new population are different from those of the old.

Gene Flow

Breaks “No Migration” rule. Organisms migrate, leaving their population and moving to a new one, which alters the allele frequency of both. It reduces differences between populations by introducing new variations.

Sexual Selection

Breaks “Equal Mating Opportunities”. This is when certain traits influence the mating success of an individual (not environment), through secual dimorphism. It produces traits that are a compromise between selective pressures.


1. Females choosing mates that are the most colourful, best song, mating ritual etc.
2. Male vs. Male competitions where males possess physical features which lets them establish control of and defend territory against other males.

Sexual Dimorphism

Physical and behavioural differences between males and females.

Patterns of Selection

Breaks “No Natural Selection” and “No Mutations” rule. When environmental conditions make patterns in the selection process.


1. Stabilizing
2. Directional
3. Disruptive
4. Cumulative

Stabilizing Selection

Once species become adapted to their environment for a long time, selective pressures prevent them from changing. It exaggerates types ost favoured by the environment.

Graph: middle & narrow

Directional Selection

An environmental change tiggers it because there are new forces of selection. It favours individuals with a more extreme variation of a trait.

Graph: Move to one side

Disruptive Selection

An environmental change tiggers it because there are new forces of selection. It favours individuals with variations at opposite extremes.

Graph: Higher at each sides and dips in middle

Cumulative Selection

Beneficial mutations that are slowly accumulated.

Artificial Selection (Mechanisms)

Breaks “Equal/random Mating Opportunities” rule. Humans choose who breeds with who and which genes are passed down.

Microevolution

Evolution occuring at the species level (within).

Macroevolution

The formation of a new species.

Species

Can interbreed and produce a fertile offspring.

Allopatric Speciation

When a species is geographically separated and the selective pressures are different, resulting in a new species.

Sympatric Speciation

When a species is reproductively isolated but there’s NO geographical separation.


1. Prezygotic: Before fertilization. Mating is prevented because of different niches, different mating seasons, wrong mating behaviors or wrong reproductive structures.
2. Postzygotic: After fertilization. prevents interbreeding due to different numbers of chromosomes. Offspring is unlikely to be born, but if it is, it’s a hybrid who is unlikely to survive long and is infertile.

Derived Characteristic

An uncommon trait or characteristic that is not shared among two groups. (a trait that is present in a particular species or group of organisms but not in their common ancestor because the species has evolved)

Mass Extinction

A pathway of evolution where a significant amount of earth’s biodiversity is wiped out in a relatively short period of time.

Rate of Evolution: Gradualism

Theory that states large evolutionary change in species is attributed to the accumulation of many small changes. Because of this there should be many “transitional forms” but there’s not, which people believe is due to holes in the fossil record.

Rate of Evolution: Punctuated Equilibrium

A theory that attributes large evolutionary change to relatively rapid bursts of change followed by long periods of little to no change. Says speciation occurs in small isolated populations which means there are rarely transitional forms.

Divergent Pathways

Two or more species evolve from a common ancestor and have increasingly different traits resulting from selective pressures and genetic drift. Leads to homologous structures.

Rapid Divergence (adaptive radiation)

Divergent evolution in rapid succession or simultaneously.

Convergent Pathways

Two or more distantly related species become similar in response to similar pressures. Leads to analogous features.

Coevolution

Two unrelated organisms act as selective agents to each other. (cause each other to evolve)

Altruism

A form of coevolution where the behaviour of one organism benefits another at a cost to itself.

Kin Selection

Behaviour that enhances the success of closely related individuals, thereby enhancing the first ones fitness indirectly because they share more genetic material.