Evolution is the central concept that unifies all of biology so understanding it is absolutely crucial if you, want to understand animal behavior
evolution and natural selection one process through which evolution occurs
Provides us with the way to answer deep questions about, why animals behave the way they do for
Example why an animal might group with others rather than being solitary a
Way it chooses more brightly colored mates a white sings to claim a territory
Without evolution the sillier of animal behavior, would be limited to simply cataloguing, what animals did
in
The most simple terms when, we talk about biological evolution, we mean descent with modification
This, means the individuals pass on their traits to their offspring but at the distribution of traits within a population changes over time
We can, follow, this process from generations generation?
By looking at changes in the gene frequency of a population as genes are the, main way that traits are passed from parents to offspring
Over many generations, these changes accumulate leading to new species arising and diverging from each other
Biological evolution is based on the idea that all life on earth shares a common ancestor that gave rise the tremendous diversity
Of animals plants and other organisms, we see today
Animals alone comprise a vast number of species more than
67,000 vertebrate species and over 1.3. Million invertebrate species have been discovered since humans started recording them
There are certainly many others still undescribed
All life is related
The question is just a matter of degree in the same
Way your parents are a common answer ancestor between you and your siblings and your grandparents a common ancestor between you and your cousins
We can, identify a common ancestor between us and any other species on earth
For some species such as chimpanzees that now extinct common ancestor lived only a few million years ago a
short time compared to the history of life
To, find our common ancestor with all with all the rest of the prime it's requires going
Back tens of millions of years and the last common ancestor of all mammals probably lived around
160 million years ago in
These terms our cousins are species like dogs and cats, which are alive now
But are more closely related, to each other than either are to us
Species that share more of their evolutionary history should be more similar so by, studying inherited characteristics across species, we can reconstruct
their evolutionary relationships, we call, these relationships of phylogeny
When reconstructing, phylogenies, we need, to be careful, we look at the right traits as not all shared traits are a result of inheritance
Sharks, dolphins, and extinct if the ichthyosaurs all look
Very similar but these are not indicators of closely relation airi relationships just adaptations to being a. Successful marine predator
Shared traits that are attributable to inheritance are called homologous
While those that evolved independently through convergent evolution are analogous
So, we know that species are related to each other by different degrees
But what causes species to change in diverged the modification part of descent with modification
There are three, main processes mutation genetic drift and natural selection
Mutations occur when genetic material is improperly copied or damaged by environmental factors
Mutations are random and most either do nothing or negatively affect the organism, by disrupting an important biological function
For some mutations are beneficial creating
New traits or modifying existing ones and this creates variation in the population as mutants, pass on their traits
An example of a mutation that, would generally be harmful in the wild is leucism loss of pigmentation such as in this peacock?
But perhaps a leucistic mutant of a different animal would benefit from having less pigmentation for example if it lived in a snowy region a
Second source of evolutionary change is genetic drift
This is a random process that occurs because there's always a look components to reproduct
If an individual gets lucky and leaves a lot of descendants the next generation will have a disproportionate share of its traits
Drift is particularly important in small populations as a run of bad luck or good luck can lead to traits going extinct with
No, carriers or being fixed, which means everyone has the trait
The, final process of evolution is natural selection first described by charles darwin, and alfred russel wallace
Unlike mutation and drift
Natural selection is a strictly non-random process that occurs because different traits lead to different reproductive success
Natural selection explains how, the traits of animal populations change to suit their environment a process we call adaptation
The logic of selective natural selection goes as follows
Firstly, there's variation within species this, means the individuals differ in their physiology morphology or in their behavior
Secondly, some of this variation is heritable offspring tend to be more similar to their parents than to other members of the population
Thirdly, many offspring are produced but populations remain
A similar size, so there's competition between individuals for resources such as food space or mates
fourthly
Some variants are better at competing than others so over time the proportion of the successful variants in the population
increases and
Fifthly environments are variable and they can change so different variants are successful in different times and places
From this it follows that the traits present in any population will gradually converge on whichever traits are best at surviving
Competing and reproducing in the current environment
If two populations of the same species become isolated from each other their traits will gradually diverge especially if their environments differ
let's illustrate, this graphically
Imagine you have a population of animals in which a mutant trait arises
The mutant conveys an advantage so it spreads through the population with each generation
Eventually becoming very common
But what if that original population?
Was divided into two
For example, by a natural barrier such as a mountain range if
different beneficial mutants arise in each population and
Then spread the populations will gradually diverge in their traits
Natural selection is constantly optimizing traits so into stable conditions, we expect. Populations to be well adapted to their environment however
individuals within populations
still vary
We use the word fitness to describe how. Good a particular individuals traits are leaving descendants relative to others in the population
fitness has
Defined with respect to a
Particular genotype or phenotype in a given environment and is measured by the relative
Contribution of an individual of that type to the next generation
What does all this mean for studying behavior?
In short because of the action of natural selection, we know animals will generally behave to optimize, their fitness
if we want to understand them, we first need to focus on understanding how that behavior relates to helping them, survive or leave descendants and
If we want to influence their behavior?
We need, to use our understanding of their natural environment and how. They interact with it to figure out. What's likely to work
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