CAS: Evolution & Domestication

What is DNA?

The 'code of life' made up of four base pairs: A, T, G, C.

What is a gene?

The basic unit of heredity composed of DNA.

What is an allele?

A variation of a gene.

What do proteins denote in an organism?

Functional units that determine an organism's functions and features.

What is evolution?

The process where heritable traits change through numerous generations.

What is genetics?

the genes (DNA) that allow for the passage of traits from

parents to offspring

What are heritable traits?

Traits that can be passed genetically from parents to offspring, very small traits

What are mutations?

Heritable changes that occur in genes (DNA) that can have negative, neutral, or positive effects, usually negative

chromosomes crossed, or some environmental factor changed the plans

These mutations occur in the egg and sperm cells created by the parents

• The genes (DNA) the parents pass to the offspring contain mistakes

How do beneficial mutations affect a population?

overtime, the percentage of offspring that inherit the favorable trait over generations increases through natural selection
this creates variation in traits

Visualizing the change in the species takes many mutations over a VERY long period (evolutionary change is VERY slow)

What is fitness in evolutionary terms?

The ability of an organism to survive, locate food, shelter, reproduce, and care for young.

To evaluate fitness, you need to know:

• Did animal survive?

• Locates food, shelter, avoids predation

• How many offspring did animal have?

• Animals with high fitness pass on more genetic material to next

generation

Who hypothesized the theory of evolution?

Charles Darwin hypothesized (now scientific theory) that all life traces back to a common ancestor, natural selection is the mechanism by which life evolves

What is natural selection?

The process where specific traits determine whether an organism lives and reproduces.

• Natural selection is the process where the specific traits of an organism determines whether it lives and reproduces or dies and does not reproduce

• NOT artificial selection (selective breeding)

How does evolution respond to the environment?

Evolution occurs as a response to environmental changes, not in a specific direction.
• Evolution is NOT moving towards “humans” or in a specific “direction”

Generally, populations of a species remain stable over time

• Due to natural selection!

• Specific species may have fluctuations due to mating seasons/reproductive cycles but overall, the populations are surprisingly stable over long periods of time

What is the significance of heritable traits in populations?

They increase the survival of offspring and are passed down, affecting species over time.

What does 'survival of the fittest' mean?

It refers to passing heritable traits to as many successful offspring as possible.

Survival of the fittest focuses on passing heritable traits, via reproduction, to as many offspring as possible

What factors influence natural selection?

dominance hierarchy, territories, access to food/water/resources, approval of females, etc.

• Most factors are much more indirect such as ability to find and use food, resistance to environmental stress

(temperature, predators, weather, etc.), and effective growth and development

What is the mark of evolutionary success?

The number of successful offspring produced, not just the total number of offspring.

• A smaller number of successful offspring is evolutionarily more significant than having many unsuccessful offspring

• Quality > quantity

What is competition in evolutionary biology?

The struggle for resources such as food, water, and mates among individuals of a species.

How does natural selection drive evolution?

It leads to changes in species over generations based on heritable traits.

What is required for evolutionary change?

Differences between offspring; if all offspring are the same, evolution cannot occur.

all offspring will differ, leading to infinite possibilities of genetic make up of offspring of two parents

Why is variation in species important?

It allows for responses to environmental changes and contributes to evolutionary processes.

What is the relationship between natural selection and evolution?

Natural selection is the mechanism by which evolutionary change occurs over time.

What are the effects of most mutations?

Most mutations are harmful to the body.

What is the role of minor changes in evolution?

They accumulate over time to lead to significant evolutionary changes.

What is the difference between natural selection and artificial selection?

Natural selection occurs without human intervention, while artificial selection is selective breeding by humans.

What is the importance of genetic variation?

It provides the potential for adaptation and survival in changing environments.

What is a major contributor to evolution?

Environmental factors

What leads to selection pressure in evolution?

Changes in the environment

What happens to heritable traits under selection pressure?

They may become more or less common.

How does evolution occur over time?

It occurs slowly over millions of years.

What is the process of evolution in response to environmental changes?

Evolution occurs until the environment and population stabilize.

What is the nature of evolutionary change?

It can occur without dramatic changes or catastrophes, doesn’t need dramatic mutations, not random natural selection: towards order

What is the difference between evolution and natural selection?

Evolution is a slow process of change, while natural selection is a mechanism that drives evolution towards order

What is artificial selection?

Humans influence offspring traits through selective breeding.

What is domestication?

An evolutionary process via artificial selection driven by humans.

• Changes in anatomy, physiology, behavior, etc.

• Based on HUMANS selecting the heritable traits in the offspring – NOT natural selection

• Massive effect on human societies

• Domestication changes the species from its ancestors to benefit humans

How does domestication affect species?

It changes anatomy, physiology, and behavior to benefit humans.

What are some early purposes of domestication?

Religious and economic purposes, such as sacrifices and labor, food, clothing, tools, hunting, etc.
• Companionship, aesthetics, behavior, livestock production, etc.

• Intentional or not

Multiple hypotheses related to how the domestication occurred

• 1. Close association with humans

• 2. Capturing and selectively mating animals

• 3. Capturing young animals and raising them with humans

• The animals best adapted to the benefit of humans were mated

What is the relationship between artificial selection and domestication?

• Artificial selection (selective breeding) used by humans to domesticate species over thousands of years

• Today, most domestication of species is related to aesthetics as opposed to functionality

How genetics affect domestication?

Examples of how genetics affect domestication

• 1. Inbreeding

• 2. Genetic drift

• 3. Artificial Selection

What is inbreeding?

Mating closely related animals, leading to a more homogenous population. Creates a more homogenous population of offspring

• The offspring are more similar and have less variation

What is genetic drift?

A change in genetic variation in a population due to chance.

• Not due to natural selection (or sometimes even artificial selection)

• Positive OR negative heritable trait becomes the common trait in the population

• Most common in small populations

What is the difference between domesticated and tame animals?

Domesticated refers to permanent genetic changes that can lead to predisposition to associating with humans (applies to whole species), while tame refers to individual conditioned behavioral modification at the individual animal level

What is feralization?

The process where domesticated species revert to natural selection after removal from artificial selection.

Domestication in the “opposite” direction

• Over time, the species may become “wild”

• If the animals still have traits related to their domestication, they are considered feral animals, yes

pigeons, cats, dogs

What are some physical changes in domesticated animals?

Increased variation in coat color and changes in body size.

Select for extreme heritable traits/characteristics

• Depending on the heritable trait, will require human intervention for breeding and reproduction

• Decrease in competition due to humans providing resources allows for heritable traits that are not “ideal”

• Reduced ability to respond to changes in the environment, not fighting for food, or need to sharpen claws

• Changes to behavioral traits

Changes to Domesticated Animals

Physical

• Increased variation in coat color, horns, hair coat

• Decrease in ratio of brain size to body size

• Change in body size

• Skeletal changes (shortening of jaws and facial region,

reduction in size of the teeth)

• Physiology

• Faster growth rate & changes in pattern of fat deposition

• surplus fat tends to be deposited throughout muscle in

domestic species and around internal organs in wild species)

• Increased muscle, milk production, or other economically

favorable changes

What is neoteny?

Retention of juvenile characteristics in adults, a major genetic change of domestication.

floppy ears, changes in reproductive cycle, curly tails, piebald coloration,

fewer or shortened vertebra, large eyes, rounded forehead, large ears, and shortened muzzle

What are some behavioral changes in domesticated animals?

• Loss of self sufficiency

• Less adaptable to changes in environment

• Loss of pair bonding (ducks, geese, foxes)

• Loss of broodiness in chickens and turkeys

• Reduced flightiness and aggressiveness

• Increased juvenile characteristics

• Less fearful towards humans

• More socially tolerant of conspecifics

DOMESTICATION IN HISTORY

• Remember, domestication is the long over time process of

evolution via artificial selection (selective breeding)

• Three major (companion animal) species:

• Dogs

• Cats

• Horses

• Most recent (last) common ancestor – the most

recent ancestor that gives rise to a specific group

of organisms

• Ancestors from domestication occurred based on

artificial selection (related to human environments,

locations, etc.)

What is the common ancestor of dogs?

The gray wolf (extinct), 15 to 17 thousand years ago.

Domestication of the dog related to benefiting the human based on location, environment, etc. via artificial selection

Dog domestication

Dogs are omnivores (leaning towards

carnivorous diets) – thus they compete

with humans

• Domestication likely related to hunting and

retrieving abilities

• Domestication of dogs WAS NOT originally

for companion purposes

• The domestication of dogs is changing 

artificial selection is geared towards

companion animals

• Small, docile dog breeds becoming much

more common

What is the common ancestor of cats?

“Cat common ancestor” – European and African wildcat

• Domestication of cats occurred around 9,000 years ago

Cat domestication

Cats are obligate carnivores and would be in competition with humans…

• BUT it is important to note the prey species of cats 

• Cats could protect human dwellings, places where food is stored, etc. from rodents

• Rodents eat the food

• Rodents contaminate the food

• Rodents carry diseases and pests

• The domestication of cats was likely related to a mutually beneficial relationship

• The humans store food, have dwellings, etc. that attract the rodents

• Cats have a great hunting area while assisting humans in protecting their food and buildings

• Cats more easily undergo feralization compared to dogs

• Artificial selection in cats focuses more on physical features in the current era

What is the common ancestor of horses?

“Horse common ancestor” - Eohippus

• Horses are estimated to have been domesticated around 4,000 years ago

Horse domestication

Horses are herbivores leading to a different domestication pattern

• Horses were first domesticated for consumption

• Horses were then domesticated to pull carts and to be ridden

• This increased the horse's significance in war  completely changed warfare!

• Horses allowed humans to move over larger areas of land more easily

• Horses pull large loads

• Horses were used for sport (racing, riding, etc.)

• Horses today are domesticated for the specific “job” they perform

• Pulling, racing, jumping, show, pleasure riding, etc.

What were horses initially domesticated for?

For consumption and later for transportation and warfare.

What are the implications of domestication on human societies?

It has massive effects, changing species from their ancestors to benefit humans.

What role does artificial selection play in the exotic pet business?

It influences physical features and traits of animals.

What should potential pet owners consider regarding domestication?

The animal's domestication history and the ethics of sourcing pets.