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Family connections: genes and heredity. From yesterday:. What is evolution?. From yesterday:. What is evolution? The process of genetic change in populations of organisms over time. What is necessary for evolution to occur:. Three things:. Organisms multiply in number (“reproduce”)

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three things

What is necessary for evolution to occur:

Three things:
  • Organisms multiply in number (“reproduce”)
  • Children tend to resemble their parents
  • Not everybody is the same
natural selection1

Mechanism by which evolution works:

Natural selection
  • Variation between individuals: some are more likely to survive than others.
  • Some variation is heritable, since children tend to resemble their parents
  • Next generation resembles those who did best in previous generation
  • Given time, lots of small changes add up to make large changes
evolution by natural selection also explains why

What is evolutionary theory good for?

Evolution by natural selection also explains why:
  • Organisms become good at what they do: “adapted” to their environment & lifestyle
  • In many cases historical contingencies prevent “optimal” adaptation: “bad design”
  • Organisms have changed over time, as evidenced by fossils
fossils show transitional forms

Thus, fossils are another piece of evidence for evolution

Fossils show transitional forms

For any major changes in animal form, we have fossils that show the transitions

“Archaeopteryx”

fossils show transitional forms1

What is evolution?

Fossils show transitional forms

For any major changes in animal form, we have fossils that show the transitions

“Tiktaalik”

evolution by natural selection also explains why1

What is evolutionary theory good for?

Evolution by natural selection also explains why:
  • Organisms become good at what they do: “adapted” to their environment & lifestyle
  • In many cases historical contingencies prevent “optimal” adaptation: “bad design”
  • Organisms have changed over time, as evidenced by fossils
animal family trees

Other evidence for evolution

Animal “family trees”
  • Some classification works better than others
  • The ones that work all give the same result!
  • I.e. the number of legs, the type of skeleton, the genetic similarity, all give the same consistent “family tree”
biogeography

Other evidence for evolution

Biogeography
  • Every species of plant or animal originates somewhere. It then may spread, but not if there is an ocean in between!
  • How organisms have spread at different times agrees with what we know about continental drift.

Americas:

  • Tomato plant
  • Teosinte/Corn
  • Potato plant
  • Turkey
  • Saguaro (almost all cacti)

Eurasia:

  • Starling
  • Elephant
  • Honey bee
  • Euphorbia plants
summary what evolution is
Summary: what evolution is

Variation, Natural selection, and Inheritance leads to change in a population over generations

  • A logical consequence of what we know about heredity & survival
  • An explanation for the appearance of design in living things (adaptation)
  • An explanation for many other observations that would otherwise seem random coincidences
  • The intellectual framework for all of biology & medicine

Joanna Masel: What evolution is and what it isn’t

slide14

Heredity & genes

Evolution requires inheritance of traits. We know today that traits are inherited via genes.What is a gene, and where are the genes in the body?

animals and plants are built of thousands of cells

Heredity & genes

Animals and plants are built of thousands of cells

(~50 trillion in a human)

- and each one contains your whole genetic material!

what else is in a cell

Heredity & genes

What else is in a cell?
  • Membrane
  • Genetic material
  • Machinery
important molecules in the cell

Heredity & genes

Important molecules in the cell
  • Proteins: enzymes (machines), actin filaments (skeleton, transport)
  • Lipids (build membranes)
  • DNA (information/blueprint to build proteins)
slide20

Enzyme copying DNA

DNA double helix

chromosome

genes

Heredity & genes

Genes
  • Each cell contains a complete copy of an organisms genome on a long strand of DNA
  • A “gene” is a section of DNA that gets translated into a protein
  • Proteins make up machines, skeleton, and color of cells  and therefore determine form and function
genes1

Heredity & genes

Genes
  • Humans probably have about 30 000 genes – other animals can have fewer or more
  • Similarity between parents and offspring – “heritability” – is a result of genes: each child gets a copy of some of the mother’s and some of the father’s genes.
gregor mendel

Heredity & genes

Gregor Mendel
  • A monk who grew peas
  • Discovered that inheritance is based on discrete units (which were later called “genes”)
two genes for every trait

Heredity & genes

Two genes for every trait
  • One from mother, one from father
  • Some are dominant, others recessive

RW

RW

RR

WW

two genes for every trait1

Heredity & genes

Two genes for every trait
  • One from mother, one from father
  • Some are dominant, others recessive
  • In humans, blue eyes are a recessive trait, brown eyes are a dominant trait

If my dad has blue eyes, what is my eye color? (What is my brother’s eye color?)

neurons nerve cells

Heredity & behavior

Neurons (=nerve cells)
  • Transmit and process information
  • Connect to sense organs and muscles
  • Brain is an aggregation of neurons
how is the network created

Heredity & behavior

How is the network created?
  • During development, neurons grow along certain paths
  • Experience influences the connections neurons make
heritability of behavior

Heredity & behavior

Heritability of behavior

Behavior can be heritable,

  • because the formation of the brain and specific circuits, even the potential to learn, all require information before learning: genetic information.
  • Any variation in that genetic information is heritable.
very complicated behaviors can be determined by genes and thus be heritable and evolve

Genes and behavior

Very complicated behaviors can be determined by genes (and thus be heritable and evolve)

There is plenty of evidence for this, even though we don’t always understand exactly which genes influence which neurons, and in which way.

exp 1 solitary animals cannot learn from parents or conspecifics

Genes and behavior

Exp 1: solitary animals – cannot learn from parents or conspecifics

Fiddler crabs: ‘wave’ to attract females, build burrows in mud to hide at high tide

exp 3 human infants can do many things

Genes and behavior

Exp 3: human infants – can do many things

Infants know that two piles of sand poured in a bucket can be made into any number of sand piles, but two dolls in a bucket are still two dolls afterwards

exp 3 human infants can do many things1

Genes and behavior

Exp 3: human infants – can do many things

Infants know that two piles of sand poured in a bucket can be made into any number of sand piles, but two dolls in a bucket are still two dolls afterwards

exp 4 breeding studies if animals can be bred to do something it must be heritable

Genes and behavior

Exp 4: breeding studies – if animals can be bred to do something, it must be heritable

Swallows were bred to fly south or west; honey bees can be bred to hoard more or less pollen; dogs were bred to retrieve or point

slide38

Genes and behavior

And why not cats??You cannot teach a cat to herd sheep, because it is genetically different from a Border Collie
evidence that behavior is heritable

Heredity & behavior

Evidence that behavior is heritable

Many kinds of evidence!

  • Artificial selection / purebred strains / twin studies
  • Specific genes identified / heritable malfunction / mutants
  • Differences between species if raised in lab under same conditions
however many traits are not heritable

Heritability vs. aquired traits

However, many traits are not heritable!

Why? Because

  • Developmental effects
  • Plasticity
  • Learning

can cause differences between individuals.

however many traits are not heritable1

Heritability vs. aquired traits

However, many traits are not heritable!

Why? Because

  • Developmental effects
  • Plasticity
  • Learning

can cause differences between individuals.

NO evolution of these differences!

genes2

Heredity & genes

Genes
  • Each cell contains a complete copy of an organisms genome on a long strand of DNA
  • A “gene” is a section of DNA that gets translated into a protein
  • Proteins make up machines, skeleton, and color of cells  and therefore determine form and function
summary what evolution is1
Summary: what evolution is

Variation, Natural selection, and Inheritance leads to change in a population over generations

  • A logical consequence of what we know about heredity & survival
  • An explanation for the appearance of design in living things (adaptation)
  • An explanation for many other observations that would otherwise seem random coincidences
  • The intellectual framework for all of biology & medicine

Joanna Masel: What evolution is and what it isn’t