Evolution Basics Flashcards
microevolution
genetic changes in a species/population of living things over generations
- requires optimal fitness which means adaptation to its environment
macroevolution
speciation and extinction
evolutionary Medicine
evolutionary methods used to understand disease and medicine
4 Key forces of Evolution
variation
selection
population genetics
culture
variation
mechanism for evolutionary change and has selective advantages
- example: skin pigmentation
mutation
- # 1 mechanism for variation
- most are neutral recessive or silent b/c variation must be compatible with life
- leads to new traits/diseases
certain genes are highly conserved across species b/c………..
they play a major role in body functions so not usually mutations here since it could cause death
- ex: HOX gene
- mutations happen in less crucial genes so its more compatible with life
fixed alleles
all other versions of the gene die out except for one, so a whole population could share that one gene
sexual reproduction
- 3 ways to get genetic diversity
sexual reproduction ensures genetic diversity and integrity through meiosis
1. independent assortment (chromosomes)
2. random fertilization: high # of chromosomes in egg/sperm
3. recombination: during meiosis swap genetic material to create variation
Skin Pigmentation
- folate and Vit D hypothesis explains the evolution of skin pigmentation
- UV light catalyzes synthesis of Vit D precursor in the skin from dehydrocholesterol
- used for bone development and calcium metabolism
- excessive UV exposure causes photolysis of folate and it’s deficiency
- less sun = need to absorb more UV light = less pigment = lighter skin tone
- more melanin = darker skin = more protection from UV rays so protects from folate depletion
3 Types of Selection
artificial: minimal genetic engineering or selection for certain traits by humans on other animals like dogs
natural: competition between and within a species and the environment restricts population growth
sexual: different sexual success within one species
4 effects of natural selection
- positive (bigger) or negative (smaller): like giraffe neck length increasing is +
- stabilizing (birth weight: which is associated with diabetes )
- balancing (ex: sickle cell anemia homo=bad, hetero=good)
4 disruptive which is selective against the mean (Darwin’s finches beaks became large or small depending on food source)
sexual selection
- Intrasexual competition
- leads to sexual dimorphism
one constraint is natural selection, like in peacocks if the tail is to large you cant run from predators - ex: male mortality
example of sexual selection
male mortality:
- males evolved to compete with other males to demonstrate they are the optimal mate but humans also live in a stable social group
- women live longer than men due to extrinsic causes like violence/aggression, smoking/alcohol, risk taking behavior
population genetics mechanisms
migration: certain ethnicities are prone to certain diseases /mutations b/c o genetics
gene flow: ppl carry alleles in their genome as the move from place to place
genetic drift: allele changes occur due to a random event
- founder effect: a population moves to a new area but the gene pool becomes limited
- bottle neck: large gene pool but an event happens where only a few survive and procreate to make a new population
culture
- socially learned behaviors that differ between cultures
- creates selective pressures (gene culture evolution) like lactase persistence
- its rapid and influences our biological evolution
lactose tolerance
- Due to pastoralism diary is introduced to the diet post weening of children so the mutation that allows us to consume dairy is advantageous
- If lactose intolerant the bacteria will ferment the lactose and increased osmolarity draws water into the intestine causing bloating, diarrhea, cramps
- Evolutionary Convergence
Evolutionary Convergence
similar traits are naturally selected for in different populations/areas in different ways that are independent of each other
6 fundamental principles of evolution
- environmental influence
- evolution has no specific goal
- adaptation
- sexually selected traits
- fixed mutations: neutral mutation of genetic drift
- exaptation: a specific trait is selected for a specific purpose but now that trait is used for a new purpose(not OG one). Like feathers are originally for heat but used for flying later
what is adaptation?
what are 3 types of adaptation?
a trait that promotes fitness and has a specific function which is driven by natural selection
3 types
1. Anatomical: physical change (bipedalism)
2. Physiological: body actions changed (shivering to keep warm)
3. Behavioral (child more dependent on mother so monogamy and parental care)
macroevolution and adaptation
adaptation occurs over many lifetimes where organisms adapt to their environment
adaptability
an individuals ability to make physical changes within their lifetime and is influenced by their evolutionary history
environments are constantly changing
- Adaptability is important because new stressors appear so traits best suited for that environment survive
- Environments aren’t constant like currently
- Population growth affects change in social and cultural environments
5 Evolutionary Constraints
- limits on physical processes: increased body size is constrained by amount of nutrients available, gravity, perfusion, movement (ppl from islands are smaller b/c less nutrients)
- evolution incrementally works over a very long time scale (ex: bipedalism causes risk for herniated disks and plantar fasciitis since body hasn’t fully adjusted to being upright)
- Mismatch between environment and rate of adaptation/selection processes (ex: we are adapted for famines but now have food surplus so obesity epidemic)
- selection operates on phenotype: many genes affect the phenotype
- exaptation &/or chance results can occur
co-evolution
- No species lives in isolation from others
- Definition: 2 species have a reciprocal relationship because of selective pressures that affect both
- This can lead to an arms race where both species continually evolve to stay fit
- Ex: human immune system and bacteria
evolution has no specific direction
- Species evolve to be successful in their specific environment
- It’s not survival of the fittest but there are drivers like natural selection and environmental changes
taxonomy
study of how organisms are classified and Classify species based on their characteristics, Carl Linnaeus
homologous
similar structures with same evolutionary history but doesn’t necessarily have same function
analogous
different structures with similar adaptation/function with NO common evolutionary history
- ex: convergent evolution and lactose tolerance
biological species concept
interbreeding individuals that are reproductively isolated from other such groups
biological species concept example
ligers can be artificially bred in captivity but don’t produce fertile offspring and are isolated from each other in their natural habitats, so they are 2 diff species because they are reproductively isolated
