Survival of the Fittest - Science of Life - 2022

Darwin's Theory of Evolution

all species of organisms arise and develop through the natural selection of small, inherited variations that increase the individual's ability to compete, survive, and reproduce.

Lamarck's theory

individuals can acquire traits during their lifetime and pass them onto their offspring

Darwin's contribution to evolution

natural selection

Evolution

the gradual change in the genetic material of
a population of organisms over a period of time.

Process of natural selection

Mutation/variation > best adapted > more likely to survive & breed > pass genes on to offspring.

selection pressure examples

- climate change
- predators, disease
- competition
- the availability of food

Why is variation important?

The more variation within a species, the more likely it will survive

what are the sources of variation in a population?

mutation, genetic drift, and gene flow

survival of the fittest

also called natural selection. Process by which individuals that are better suited to their environment survive and reproduce most successfully;

Peppered moth example

originally, the majority of these moths were light-colored, due to natural selection and then when the trees turned black due to the Industrial Revolution in England, the black colored moths came into the majority because of natural selection

Galapagos Finches

beak shape is determined by the availability of food

Species

A group of similar organisms that can breed and produce fertile offspring.

Speciation

the formation of new and distinct species in the course of evolution.

speciation mechanisms

allopatric, sympatric, parapatric

process of speciation

variation, isolation, selection

mechanical isolation

Morphological differences can prevent successful mating

gamete isolation

sperm cannot reach or fertilize egg

Behavioural isolation

when two populations are capable of interbreeding but have different behaviours such as courtship rituals or feeding.

ecological isolation

species occur in the same area but occupy different habitats

geographic isolation

form of reproductive isolation in which two populations are separated physically by geographic barriers such as rivers, mountains, or stretches of water

temporal isolation

form of reproductive isolation in which two populations reproduce at different times

pre-zygotic isolation

mating and fertilization are prevented (no zygote formed)

post-zygotic isolation

mating occurs, but offspring are sterile or die early

Hybrid

Offspring of crosses between parents with different traits

example of hybrid

mule

How does a new species evolve?

1. a population of the same species gets isolated by a barrier
2. the isolated populations are exposed to different selection pressures
3. over time enough differences build up in the two populations until they form new species (cannot interbreed)

How to identify the same species?

can reproduce and produce fertile offspring

Extinction

complete disappearance of a species from the earth

How does extinction occur?

- unable to adapt
- competition
- increased predator
- change in environment

convergent evolution

Evolution toward similar characteristics in unrelated species

evidence to support convergent evolution

example the different structure internally for fins on sharks, penguins and dolphins, but a similar look and function.

divergent evolution

when two or more species sharing a common ancestor become more different over time

evidence for divergent evolution

homologous structures

homologous structures

Structures in different species that are similar because of common ancestry.

examples of homologous structures

bones of a cat, human, whale, and bat are similar but have different functions

analogous structures

Body parts that share a common function, but not structure

Example of analogous structures

The wings of a bat and the wings of a dragonfly

comparative embryology

the study of the similarities and differences in the embryos of different species

Evidence of Evolution

1) Fossil Record
2) Embryology
3) Homologous Structures
4) DNA
5) Vestigial Structures

Biogeography

Study of past and present distribution of organisms

vestigial organs

organs that serve no useful purpose for the organism; these suggest that sometime in the past they were useful

example of a vestigial organ in a human

appendix

example of a vestigial organ in an animal

Pelvic bones of whales

Why do vestigial structures still exist?

They may have been used for previous generations but due to a change in the environment, may not have been needed for future generations.

evidence from nucleotides or amino acid sequences for evolution

the more similar the sequence, the more closely related the organisms are (same for both amino acids and nucleotides)

DNA hybridization

The annealing of a single-stranded DNA molecule to a complementary sequence

Name of Lamarck's theory of evolution

Theory of Acquired Characteristics

Fossils

Preserved remains of once-living organisms

different types of fossils

cast, imprint, mold, trace

relative age

The age of a rock compared to the ages of other rocks

absolute age

the number of years since the rock formed

difference between relative and absolute dating

Relative age is the age of a rock layer (or the fossils it contains) compared to other layers. Absolute age is the numeric age of a layer of rocks or fossils.

How is absolute age determined?

radiometric dating

half-life

length of time required for half of the radioactive atoms in a sample to decay

Radioisotopes

unstable isotopes

phylogenetic tree

A branching diagram that represents a hypothesis about the evolutionary history of a group of organisms.