Evolution, Homoplasy and Homology

Theme 1

• A population of interbreeding individuals changing over long periods is evolution
• Darwin theorized that evolution proceeds through differential success in reproduction via natural selection
• Darwin's four main points:
  • Rapid population increase unless limited
  • Individuals of a species are not identical
  • Variation among individuals is inherited
  • Not all offspring survive to reproduce
• Variations among individuals impact survival and passing on characteristics, this is known as Interference

Homoplasy and Homology

• Homoplasy is a physical resemblance based on convergent evolution
  • An example is the body structures of dolphins and tuna
• Convergent evolution is the evolutionary process yielding behavioral or structural similarities among distantly related animals responding to similar ecological features
• Homology is a physical resemblance from common ancestry
• Homoplasy involves similar traits from different ancestries, while homology involves similar traits from a common ancestor
• Key differences between Homoplasy and Homology
  • Homology Origin: Common ancestor
  • Homoplasy Origin: Independent evolution
  • Homology Example: Vertebrate forelimbs
  • Homoplasy Example: Wings in bats and insects
  • Homology Reason: Shared evolutionary history
  • Homoplasy Reason: Similar environmental pressures

Ecological Niches

• Ecological niche is the unique range of environmental opportunities and challenges to which an organism adapts

Brain Size Correlations

• Strategies for obtaining food correlate with brain size and structure across species
  • Mammals eating hard-to-find food tend to have larger brains
  • Finding novel ways to obtain food relates to forebrain size in birds
• Selection pressures favored increased forebrain size, and allowed species to adapt to new environmental challenges

Shared Characteristics of Vertebrate NS

• Vertebrate NS development begins with hollow dorsal neural tube
  • Embryonic neural tube forms brain subdivisions, fluid-filled spaces (ventricular system) persist in adulthood
• Bilateral symmetry involves cerebral hemispheres as near mirror images
• Segmentation involves pairs of spinal nerves from each spinal cord level
• Hierarchical control: Cerebral hemispheres control or modify activity of spinal cord
• Separate systems: Clear distinction exists between CNS and peripheral NS
• Localization of function entails specific functions being controlled by certain CNS locations

Brain Region Differences Between Species

• Studying fossil brains, entails 2 methodologies:
  • Endocast: A skull's cranial cavity cast useful for studying extinct species
  • Studying present-day animals, and comparing them to shared similarities with the ancestral species
• Detailed info comes from studying living species rather than endocasts
• Large cerebellar hemispheres evolved independently in birds and mammals from the small cerebellum of a shared reptilian ancestor
• All mammals possess a six-layered cortex, sometimes termed as neocortex
  • Cortex: Mostly nerve cell bodies and their branches on the outer cerebral hemispheres

Encephalization Factor

• Neocortex is a six-layered cerebral cortex that is mainly responsible for higher-order functions
• Correlation occurs between body and brain weight across any species
• Encephalization factor measures brain size relative to body size
  • Deviation from mammal expectations
  • 'k' is the vertical distance on graph (above/below line)
  • Greater encephalization factor exaggerates brain size relative to mammal size
• Humans exhibit the highest encephalization factor

Explanations for Large Relative Human Cortex

• Human cortex becomes larger proportionally relative to any other body parts
  • Medulla becomes smaller relative to brain weight
  • Cerebellum growth keeps pace with brain
• Cortex has grown disproportionally over evolution
  • Expansion is due to outer cortex layers being developed last
• Developing fetal development grows the inner layers of cortex first, and new neurons are added to form each subsequent outer layer
  • Outer layers have enlarged more in primates than inner layers
• Brain regions most expanded over primate evolution develop later in life and enable complex functions
• Natural selection would favor a larger cortex

Social Brain Hypothesis

• Larger cortex handles complex cognitive task of maintaining social relationships in larger-brained individuals
• Brain size correlates with:
  • Innovations in behavior
  • Use of tools
  • Social learning
• Correlation exists between average clique size and ratio of cortex to overall brain size

Gene Expression Differences

• Genetic basis can contribute to human and closest relative differences in two ways:
  1. Specific gene DNA sequences vary between species
  2. Gene expression varies in its ability to construct a complex brain
• Humans differ from primates in brain gene expression patterns
  • Patterns have been changed and accelerated in human lineages
• A small change in gene expression can cause dramatic differences in brain development

Neuron and Glial Cells

• Neuron/nerve cell is the nervous system's basic unit
  • Includes a cell body, receptive extensions (dendrites), and transmitting extensions (axon)
• Glial cells are nonneuronal brain cells
  • Provide support to the brain and how it processes data
• Astrocytes, Microglial, Oligodendrocyte, and Schwann are main glia cells
• Glial cells communicate with each other and neurons + supply neurons with materials and signals that can alter structure

Astrocytes

• Run numerous processes/ extensions in all directions as glial cells that are shaped like stars
  • Regulate blood flow to provide more supplies to neurons during heightened activity
  • Monitor neural activity
  • Modulate the neurons output

Microglia

• Very small glial cells removing cellular debris from injured or dead cells
  • Maintains synapses

Oglio and Schwann

• Oligodendrocytes forms myelin in central NS
• Schwann cells forms myelin in peripheral NS
• Myelination is the process of forming myelin
• (3 and 4) wrap sections of the axon in multiple layers of myelin
  • Myelin improves the speed of conduction of impulses

Parts of a Neuron

• Dendrite: Extensions of the cell body that are receptive surfaces to the neuron
  • Receives information from other neurons
  • Input zone of the cell
• Dendritic Spines: Outgrowths on dendrites
  • Allows for extra synaptic contacts
• Cell body (soma) is the region of a neuron that contains the cell nucleus
  • Input combined in integration zone
• Axon Hillock: A cone area where the axon originates out of the cell body
  • This area Collects it, then converts it into a electrical impulses
• Axon: Carries messages/ electrical impulses away from cell body to neurons
  • Conduction zone
• Consists of 2 Functions
  • rapid transmission of electrical signals on axon's side
  • Transportation inside to form axon terminals
• Axon Terminal: End of axon
  • Transmits zone

Neurotransmitters

• Neurotransmitters: Molecules that share chemical composition
  • Should be synthesized and stored
  • Need to be released by the presynaptic neuron
  • Post synaptic must have specific receptor
  • It should simulate the same response
• 4 Classes:
  • Ach, aspartate, dopamine, and Neuropeptides
• Excitatory:
  • The ACh and some Neuropeptides are examples
• Inhibitory:
  • GABA and Glycine are examples

Conditional Neurotransmitter

• When it effects the other synapse

Steps in Chemical Transmission

• Potential comes to terminals
• Leads to deprotization creating an influx of ions
• Increases concentration causing transmitter to attach to synapse
• Then gets released
• The transmission occurs

After the protein is created

• Depolarization or Hyperpolarization

Protein Structures from simple to complex

• What the amino acids are
• How long for amino acids
• How the amino acids are folded
• Many protein are created to make up one

2 Classes

• Ionotropic: Channel to the ion
  • Immediate change and binding
• Metabolic: Linked to g protein
  • Advantage is quick

How neurotransmitters are synthesized

• Proteins are synthesized, the transmitter occurs

Transmission Steps in Order

1. The cell then attaches,
2. The proteins attach
3. Then it leads to the clef

Synapses can transmit

• Either, the synapse can be activated
• or be inhabited by something bad for the potential

Stahal

• Neurotransmission can be retro or classic and volume

The process of making it into an elerical or chemical impulse

• Impulse activates terminal
• Opens CA
• Casues fusioin of neurotransmiter
• Continues through channels
  • or actives internal cascade

Steps in the signaling

• Neurotransmitters binds to receptor
• Sends intracellular molecule
• Creates 3rd messangers

If it needs activated and more activated, then use

• phosphate

Gene regions need to be activated

• Regulated
• Corresponding activated

Stages that leads to the gene being tranistioning

• Early - the immediate
  • Creates "Leucine zipper" -Complex activator

To transcip genes

• Factors connect to DNAs
• Get activated
• Reuited to genes

If they are not

• then control gets dealth

Siliencing

• Leads to to them being pressed

Study

• Processes development through mitosis
• Then it migrants
• Differentiation

If it is not present at birth

• How much weight would it go up by
• glial cells are added

Learning the facts

• Factors that are learned through experiences

Migration of Neurons

-Radial and tangently

Guide to cell cohesion for molecules

• Then to apoctis

Programmed cell death

• Apoctis

Neglect gets what

• Triggers

What happen if they dont get what you supply

• Competing and you have to give up one and undergo

When keeps snaps

• By activity depends

Active receriviong get

• Keep it by not eliminated

Shape connect

• In the process of learning

Visual Context and whats needed

• Only, strong and actived are there

Chapter

• Coordatinon activity to strengthen

Expands what

• To connect

This what

• New behaviours create

When the brain grows this happens

• Brain becomes continues

The environmatl will must be

• It needed for developing

Feautres

• Will get smaller if not present
• Has effects

Pre sensory

• the brain has to set its wiring to be responded

If not correct

• Then segregator for you

They all must do what

• Work seperate

Manipulating

• Its good system to use for periods

Dominane

• In the cortex

Which does

• Show what is contriling

Alteranativly

• Input 4 of cortex

It cant do what

• Binds at a site

Derpiation

• Form normal visiob

Fewer do what

• Cells respond

If the eyes is open takes

• Over contex Territory

What happens if Both eyes have

• Bioocualr

Interpretation

• Competition

Induces strabismis

• Not related bincol

Prevents is whagt

• Convergence leads less nerurons

Same can not

• Two at time

Ablyopia

• reduced vision by input

How Does it do it

• Favors on side supress

Treatment period is

• Must do with right way the period

Transmirtted

• Glutatme and excitory

Do what at cerical

• Triggers with main

Second makes it

• Make caclium

Activation is

• In kinaes to strengh

Capaciyt is what

• Must instill dev

The represent lang

• Is langterial

Laterliazation occurs

• Alttered

Older what? and what.

• Aged are 7, declines are sharp and is

Lack is what to deaf?

• Neglegt shown defects.

Grey are what to mater

Increases what

• Increase in puberty

Decline what

• During advioles

Represent what, and leads that

• Represent circuit

Whiter what? Steady increases what?

• The mater increase in aduld to connect

Local what? what can see from this side?

• What is the main thing to see where

Is not in good what? What do you mean?

• To make brain in what it needs

Neuronal

• from

From can what it

• reactivates.

to restore

• Restore neuronas!

To Damage to brain?

• Damaget to brain

Neurons do what

• Re grow. There has to be certain distance for that to accurd

glial will?

• overgroe

new formation is called?

• to be "neurogensis"

For this to accrude It has to

• reguires stem cells, supportment, stabilization,