Unit 4 - evolution, speciation, and conservation of biodiversity

Evolution

The cumulative change in the heritable characteristics of a population.

Charles Darwin’s theory of evolution

Variation within a population leads to selection pressures, which enable organisms that are better adapted to the environment to survive and pass on this advantage to future generations. (ex. evolution of giraffes to have longer necks).

Lamarck’s theory of evolution

Evolution occurs within an individual’s lifetime due to either the changes in the use of organs, acquiring certain characteristics during a lifetime, or the effect of the environment influencing organisms to have new needs.

Why Lamarck’s theory was incorrect

As we gained more knowledge of the DNA structure and how it works, we understood that variations of organisms are caused by random mutations in DNA, which modify the DNA code. Modern genetics show that acquired biological characteristics CANNOT be inherited unless they cause a change in the organism’s DNA.

Sequence homology

When two DNA sequences are similar but not identical.

Why sequence homology is evidence of evolution

Because these sequences are similar suggests that there was a common ancestor, and from that, we can see that two or more organisms diverged from a common ancestor and became different species, accounting for minimal differences.

Selective breeding/artifical selection

Deliberate choosing of which organisms to breed in order to alter populations.

Homologous structures

Similar structures due to common ancestry.

Adaptive radiation

Evolution of a species into many different species due to adaptation to different niches.

relation of adaptive radiation and homologous structures

Homologous structures are proof of adaptive radiation because they show that these organisms once had a common ancestor, but they adapted differently because they had to adapt to different environments.

Convergent evolution

Species evolve similar biological adaptations in response to similar selective pressures.

Analogous structures

Structures of different species resemble each other superficially. They function similarly but have different evolutionary origins.

Evidence that supports convergent evolution

The fins of sharks and dolphins; they function in similar ways due to their need to be able to swim in water, but the actual structure of the fins is different.

Population

A group of individuals of the same species, living close enough to be able to interbreed.

Founder effect

when a few individuals from a larger population become isolated into a smaller population, and their gene pool differs from the source population.

Genetic drift

Describes the random fluctuations in the number of alleles in a population, and this can happen by the occurrence of alleles increasing or decreasing by chance over time.

Speciation

The process by which one species splits into two or more species.

Allopatric speciation

Speciation which occurs when two groups of organisms are spatially separated by a physical or geographical barrier.

Sympatric

Speciation that occurs when groups from the same ancestral population evolve into separate species due to temporal or behavioral isolation which provents individuals of one species from mating with another. (ex. temporal or behavioral)

Temporal isolation

Either when organisms produce gametes at different times or seasons, or when populations are active at different times of the day.

Behavioral isolation

When organisms acquire distinctive behavioral routines that don’t match with other individuals of the species (ex. mating rituals).

Hybridization

Producing offspring from two different species.

pre-zygotic reproduction isolation that prevents hybridization

Habitat differences that prevent meeting, behavioral differences, and temporal differences (ex. being fertile at different times or seasons).

Post-zygotic reproductive isolation that prevents hybridization

• Hybrids are viable but die prematurely

• infertile because the chromosomes can’t pair up in meiosis to produce haploid gametes

• they are less fertile where with each successive generation, fewer survive, leading to them eventually die out

Polyploidy

A process that results in more than two sets of chromosomes in the nuclear genome

Red queen hypothesis

Theorizes that different species will continue to adapt to an environment to keep up with their competitors and will not go extinct. An equilibrium is created so that the probability of extinction remains fairly constant over time.

Why does allopolyploid speciation occur abruptly in plants?

Because many invasive plant species are polyploids. These polyploid hybrids are generally larger in size, more fertile, and more invasive compared to the parent species.

How do polyploids form?

An error in meiosis leads to the formation of gametes with too many chromosomes. If these gametes combine, the offspring becomes ________.

examples of polyploid organisms

Salamander, watermelon, and peanuts.

Causes of the current biodiversity crisis

Pollution and disease, deforestation, urbanization, hunting/over exploitation, and alien invasive species.

Invasive species

Alien species that increase rapidly in number, having a negative effect on the environment an on native species.

difference between invasive and alien

Alien species are introduced to a non-native environment by human activity. They become invasive when they take over and become a danger.