BIO120 Lab 1

Divergent evolution

process where two groups from the same ancestral species accumulate different traits, leading to new species through adaptation

Arthro

joint

pod

legs

trait (not all traits are…)

characteristics (not all traits are adaptations)

Adaptation

A trait that contributes to fitness by improving an individuals chances of surviving or reproducing

What can an adaptation be?

Physical feature on the body (colour of wings) or behaviour (attraction to certain smells)

How do biologists use the term adaptation?

1) An adaptation (noun); describes a trait or the evolutionary process through which the trait arose

2) To adapt (verb)

What was Charles Darwins proposed mechanism for the process of adaptation?

Natural Selection; believed adaptations are fitness-enhancing traits that spread through the population through natural selection

What does it mean when an individual has higher "fitness"

Individuals possess traits that help them survive and reproduce better (leave more offspring) than others

How can fitness be measured?

The number of offspring an individual produces relative to other individuals in the population

What must traits that confer high fitness be?

Heritable (i.e passed in genes from parent to offspring)

Evolution

the change over generations in the proportion of individuals with a certain trait (advantageous)

What three criteria must be met for a trait to evolve by natural selection?

1. The trait is heritable

2. There is variation between individuals within a population for the trait

3. Variation in the trait leads to some individuals leaving more offspring in the next generation than others (i.e have higher fitness)

Not all population differences come from natural selection. What other ways?

1) genetically by random processes (genetic drift)

2) influx of migrants from other populations (gene flow)

Phylogeny

evolutionary history and relationships of a species; patterns of related ancestry

What do scientists hypothesize about for adaptations?

How the trait may have increased the fitness of individuals possessing that trait; possible function to explain why it evolved

What are the two types of adaptations?

Adaptations for viability (success in survival and acquisition for food) and competition for mates

What are examples of adaptations for viability/viability selection?

Adaptations for locomotion (movement), predator or parasite avoidance, food acquisition, shelter construction, and tolerance of ambient conditions

Explain Camouflage viability adaptation

organisms physically resemble their environment, less visible to predators (avoid predation)

Explain "life in water" viability adaptation

aquatic insects have bodies and legs specifically shaped to facilitate locomotion in aquatic environments

Explain feeding viability adaptation

adapted to particular diets by evolving specialized mouthparts

Example of 3 types of viability adaptations

1. Blue-winged grasshoppers blend in well with stones and sand to avoid predation

2. Backswimmers have hind legs that are oar-like

3. Ants have powerful mandibles, mosquitoes have a tube (stylet) for piercing and sucking, butterflies have a long proboscis (tongue) for lapping nectar from flowers

What is it called when natural selection arises from variable mating success?

Sexual selection

What does sexual selection result from?

The evolution of differences between males and females in secondary sexual characteristics

Sexual dimorphism

Difference between the sexes in the shape of size of the body; the distinct physical, physiological, or behavioral differences between males and females of the same species

Why are some structures present in both sexes?

Males and females share nearly all of their genes, so selection acting on one sex tends to act on other in some degree (ex. why do male humans have nipples?)

What are the two principle mechanisms of sexual selection?

Intrasexual competition and mate choice

What is intrasexual competition?

rivalry between members of the same sex to gain access to females ultimately enhancing reproductive success; combat (possess adaptations for fighting)

What is mate choice?

Increases the fitness of chooser by enabling it to mate only with healthy/attractive individuals; animals have adapted to the preferences of the opposite sex

Examples of Sexual Selection

Male european earwigs have large forceps to compete with other males; female widow skimmers perfer males with large brown and white patches on wings