BIO 3 - Week 5 Content

Co-option

Repurposing an existing trait for a new function

Gene duplication

A copying error creates a spare gene copy that mutates to gain new functions without losing the original job

Transcriptional regulation

Changing a gene’s expression via transcriptional factors

Homology

Traits inherited from a shared common ancestor

Convergence

Independent evolution of analogous solutions due to shared selection pressures

How do gene duplication and comparison of receptor signals create a new sense like color vision?

• Gene duplication creates extra copies of an opsin gene

• Small amino acid changes shift which wavelengths each copy absorbs best

• Opponency wires these cone cells together to compare outputs before sending signals to visual cortex

Homology

Trait maps to a single common ancestor on a phylogenetic tree and is shared by its descendants

Convergence

A trait appears independently on separate branches without being present in their shared ancestor

Sensory bias

Signals evolve to exploit pre-existing senses

Eavesdropping

Since broadcast signals are public, organisms evolve to detect them

Trait loss

Sensory hardware is expensive, so unused sense are abandoned or reallocated when they can’t add to fitness

Phylogeny

An evolutionary branching tree showing relationships among lineages and where traits were gained or lost over time

Natural selection

Increased survival and reproduction of individuals with strong traits

Co-option

An evolutionary shift in the function of an existing trait or protein

Transcriptional regulation

Altering a protein’s production by changing transcription factors during development

Sensory bias

An organism’s pre-existing sensory preference drives the evolution of signals that exploit it

Eavesdropping

Unintended receivers detect public signals

Trait loss

Evolutionary elimination of sensory structures when they can’t improve survival or reproduction

Gene duplication

A DNA copying error producing 2 versions of a gene

Echolocation

Using reflected high-frequency sounds to map objects in space

Why can’t cells deep inside a body rely on diffusion?

Diffusion is extremely slow over long distance and deep cells have constant needs so they would die

How do living organisms comply with the 2nd law of thermodynamics?

Universe trends toward disorder and living things acquire outside energy to build order and release disorder

Autotrophs

Fix their own carbon from CO₂

Heterotrophs

Obtain carbon already fixed by other organisms

C₃ photosynthesis

• one cell does everything

• avoids extra costs but suffers from water loss

C₄ photosynthesis

• Cells capture carbon dioxide and pump it into cells

• Photorespiration is eliminated

Chemical elements that make up nearly all biomass in living organisms

Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Sulfur (CHONPS)

Diffusion

Passive movement of molecules from high to low concentration

Energy

The capacity to do work

Entropy

A measure of disorder

Nutrients

Physical materials organisms build into their bodies

Fixing carbon

Converting energy from photons into chemical bond energy

Photorespiration

A wasteful reaction that depletes fixed carbon

Stoma / Stomata

Adjustable pores in the leaf epidermis bordered by guard cells

RuBisCO

Important carbon-fixing enzyme in the Calvin cycle

Biomolecules and energy

Organisms acquire chemicals and spend energy