Trophy Hunting and Evolutionary Biology

Trophy Hunting

• Trophy hunting targets the oldest, most mature animal from a population.
• It provides income for residents of the land.
• Ecotourism alleviates poverty and supports conservation.
• Trophy hunting is historically a big funder of conservation.

The Evolutionary Impact of Trophy Hunting

• Hunting and fishing regulations can target older, larger males; which reduces their ability to sire large numbers of offspring.
• Selective poaching caused a dramatic decline in elephant tusk size in two generations.
• Despite tusk size decreasing, shoulder height increased.

Natural Selection

• Darwin proposed populations change through "descent with modification" which occurs through natural selection.
• Natural selection favors individuals who leave more offspring and have improved fitness.
• Evolution is gene frequency change over time.
• Recombinations are offspring that have a different allele combination than either parent.

Darwin's Theory of Evolution

• Darwin worked on the HMS Beagle from 1831-1836, and published The Origin of Species by Means of Natural Selection in 1859.
• Darwin's theories were similar to Alfred Russel Wallace's.
• Darwin's theory of evolution notes that species become different over time through natural selection.
• Organisms have modifications that improve their fit for their environment.

Natural Selection in Populations

• Natural selection can cause populations to diverge over time.
• Populations, not individuals, evolve.

Case Study: Beak Morphology in Galapagos Finches

• Darwin's Finches on Daphne Major have beak depths that follow a normal distribution.
• Beak depth is a heritable trait.
• Daphne Major has significant climate variability.
• During an extreme drought, finches with deep beaks survived better because they could access harder seeds that remained available.
• In wet years, beak depth decreased as soft seeds were easier to access.
• This example demonstrates that the same trait can be advantageous in one environment and disadvantageus in another.

Types of Natural Selection

• Directional selection favors individuals with one extreme trait.
• Stabilizing selection favors individuals with intermediate traits.
• Disruptive selection favors individuals with extreme traits on both ends of the spectrum.

Antibiotic Resistance

• Antibiotic resistance can be viewed as directional selection.
• Mycobacterium tuberculosis has a gene that can prevent rifampicin (an antibiotic) from being effective.

Selective Breeding

• Historic selective breeding techniques were used to intentionally breed animals with desirable traits- such as breeding dairy cattle with higher milk production.

GMOs

• GMOs (Genetically modified organisms) have major goals of pest protection, herbicide resistance, and drought tolerance.
• In the US, GMO foods are regulated to the same standard as non-GMO foods, but they do not have to be labeled in the US.
• No proven ill effects have been reported in humans from consuming GMOs.
• Herbicide tolerant and Bt-transgenic crops dominate US agriculture.

Mechanisms of Evolution: Genetic Drift

• Genetic drift is a random process that affects small populations, causing unpredictable changes in allele frequency.
• Genetic drift can lead to the loss of alleles in a population.

Mechanisms of Evolution: Gene Flow

• Gene flow occurs when alleles transfer between populations through the movement of individuals or gametes.

Long-Term Consequences of Evolution

• Speciation, mass extinction, and adaptive radiation shape long-term patterns of evolution.
• Speciation is the process by which one species splits into two or more species.
• Speciation often occurs due to geographic or ecological barriers that prevent gene flow.

Speciation

• Speciation results in a reproductive barrier between the new species.

Mass Extinction

• A mass extinction event occurs when a large proportion of species worldwide go extinct in a short timeframe.
• Mass extinction events have occurred throughout history, with each one leading to changes in dominant species on Earth.
• For example, amphibians were replaced by reptiles as the dominant terrestrial vertebrates 265 million years ago, and reptiles were replaced by mammals 65 million years ago.

Sixth Mass Extinction

• Evidence suggests a sixth mass extinction may be occurring due to human activities; with many species disappearing at an accelerated rate compared to typical extinction rates.
• Amphibians are particularly vulnerable to this sixth mass extinction.

The Evolutionary History of Life

• Evolutionary trees represent the evolutionary history of a group, showing branching patterns of speciation and extinction.
• Evolutionary trees show the increase of species through speciation events, and the loss of species through extinction.