Chapter 6: Evolution of the Brain and Behavior Flashcards
Evolution
Change in the properties of a species over generations.
It was originally believed that each species was created ___.
Seperately
Speciation
Development of new and separate species.
Homology
Relationships among species; features are based on common ancestors.
Paleontology
Suggested evolution
- Found fossil similarities between current and past species.
Darwins theory is based on his…
Trip to the Galapagos Islands
What are Darwins 4 observations?
- Reproduction increases population unless factors limit it.
- Individuals in a species are not identical.
- Some variation among individuals is inherited.
- Not all offspring survive to reproduce.
What was Darwin’s major inference from his observations?
Heritable variations among individuals affect probability of surviving & reproducing.
=The probability of passing on those characteristics
What was Darwin’s major contribution?
Natural Selection
Natural Selection
The differential survival and reproduction of organisms with heritable characteristics.
Every species occupies a ___.
“Niche” in their ecosystem
Survival of the Fittest
How well a species/member of the species fits into its niche
Sexual Selection
The passing down of certain traits that enhance mating success.
Convergence
Similar traits/characteristics can develop separately and independently in different species.
What is an example of convergence?
- Bats and birds both fly
- Dolphins and fish both swim/have fins
Homoplasy
Similar features that evolved separately
Homoplasy contrasts….
Homology (features based on common ancestry)
What is an example of homology?
Seal flippers are similar to a human arm.
Analogy
Similar function
What is an example of analogy?
An elephant trunk and a human hand.
Mendel (heritability)
Created laws of inheritance
Hugo de Vries (heritability)
Stated that mutations occur
Mutations
Spontaneous changed in an organism’s characteristics
Mechanism of Inheritance
Genes are encoded in DNA which are inside all cells.
How many chromosome pairs do humans have?
23 pairs (2 copies of each gene)
Males have what type of chromosomes?
X and Y
What does it mean when genes are “conserved”?
There is little change/difference among species.
True or False: There are considerable genetic similarities among all living cellular organisms.
TRUE
Linnaeus (1700’s)
The classification of animals is based on the similarities among animals.
Taxonomy
The classification system of animals.
Phylogeny
The evolutionary history of species.
Modern classification of species consist of…
Phylogenetic closeness.
There is a ___ rate of DNA change.
constant
What can changes in DNA be used for?
Estimate when two species diverged from a common ancestor.
What are the 6 ways to choose species?
- Outstanding features
- Convenience
- Comparison
- Preservation
- Economic Importance
6.Treatment of disease
Are most animals invertebrates or vertebrates?
Invertebrates
What is the difference between invertebrates and vertebrates?
Invertebrates: Do not have a backbone
Vertebrates: Have a backbone
Do invertebrates have more or less neurons?
Less neurons but have large complexity in their NS.
How do we study evolution in the brain?
Compare the brains of species engaging in different kinds of behaviors.
What is an example of studying brain evolution?
Compare the warblers singing to their HVC size (displays song production).
HVC
Higher vocal center
What is the relationship between brain amount and importance of a function?
The more brain amount, the more important the function is.
What are examples of the brain amount and function relationship?
- Warblers: HVC size and # of songs they know
- Birds: Hippocampus size and their food storing ability
- Rats: Cortex devoted to whisker representation and their whiskers.
What are the 6 basic similarities across vertebrate systems?
- Development from a hollow dorsal tube.
- Bilateral symmetry.
- Segmentation.
- Hierarchical control.
- Separate systems (central & peripheral).
- Functional specialization
What are examples of regions that have been changed/altered?
- The midbrain optic tectum has becomes the visual reflex center in mammals.
- All mammals have a neocortex with 6 layers, but now more than 50% of the brain is devoted to the neocortex.
- Reptiles developed a 3 layered cortex, which may be similar to the mammalian hippocampus (3 layers).
Is evolution linearly oriented towards a particular goal?
No (birds and brain size)
Brain size must account for ___ size.
Body
Smaller animals have a ___ brain-body ration than humans.
Greater
Encephalization Factor
Takes into account each class’s deviation from the center line.
What do brain region proportions in primates display?
The relative importance of the cortex in primates (especially humans).
Cortex = higher cognitive functions
Regions of the brain that develop later become…
Larger
Small changes in genes lead to…
Big changes in the brain
EX: Cortex cells are added to outer layers at a later time.
What accounts for differences in primate brains?
- Protracted (later) brain development
- When genes are turned on/off
- Whether genes are turned on/off
- Where genes are turned on/off
Where do we see the largest divergence of gene expression?
In humans compared to other primates for brain related genes.
Brain Evolution: 4 Million yrs ago
Began walking on two feet
Brain Evolution: 2.5 million yrs ago
Stone tools
Social Brain Hypothesis
A larger cortex is needed to handle complex social relationships.
What are the other suggestions for brain growth (not main)?
- Behavioral innovations
- Tool use
- Social learning (observation)
- Sexual selection
Why is it difficult to get larger brains in humans?
A baby still needs to be able to fit out of the uterus at birth.
