Topic 5: Evolution and Biodiversity

Define evolution

Define evolution

changes in the heritable characteristics of organisms over successive generations.

Define fossils

1. fossils are the preserved remains of organisms and provide direct evidence of ancestral forms and include teeth, bones, shells and leaves.

Define traces

1. traces e.g. footprints, tooth marks, burrows and faeces provide indirect evidence of ancestral forms.

Define Selective Breeding

1. Artificial selective breeding is when humans intervene in the breeding of a species to produce desired traits in its offspring e.g. race horses.

Define variation in a species:

The differences in genotype and phenotype between the individuals in a species.

What is the Fossil Record?

• the totality of fossils, both discovered and undiscovered.

What 2 things have been discovered due to the Law of Fossil Succession?

1. Prokaryotes appear in the fossil record before eukaryotes so eukaryotes must have evolved from prokaryotes.

2. Ferns appear in the fossil record before vertebrate species, so plants evolved before animals.

What evidence is there to support the theory of evolution?

1. The Fossil Record and the Law of Fossil Succession show evolutionary links between species over a long period of time.

2. Selective breeding shows how desired traits can be produced in offspring based on breeding specific individuals of a species.

3. Variation in species shows how a species can evolve to survive based on environmental factors e.g. peppered moths.

Define transitional fossils

• fossils which establish the link between species by exhibiting traits common to both an ancestor and its predicted descendants e.g. evolution of dinosaurs (jaws and claws) to birds (feathers).

What is a homologous structure and what do they show?

• homologous structures are similar structures which are found in a variety of animals however the same structure has different functions.

• illustrate ADAPTIVE RADIATION as several new species diversify from an ancestral source and utilise an unoccupied niche.

What is the Pentadactyl Limb?

• any limb that has five digits

• humans = hand/fingers for tool manipulation

• birds - wings = flying

What 3 things can cause variation in a species?

1. Mutations - new alleles are formed

2. Meiosis - crossing over, random orientation.

3. Sexual Reproduction - every zygote is unique

When does exponential population growth occur?

• when there is an abundance of resources

When does a plateau in population growth occur?

• with more offspring, there are less resources so this leads to a struggle for survival and an increase in mortality rate, slowing down population growth.

Define Natural Selection

• The process by which organisms that are better adapted to their environment survive, reproduce, and pass on their advantageous alleles, causing advantageous characteristics to increase in frequency within a population.

Name an example of Natural Selection and outline what occurs:

• antibiotic resistance.

• bacteria which are exposed to antibiotic die, however bacteria which carry a resistant gene survive

• these resistant bacteria go on to reproduce, passing down antibiotic resistant DNA to its offspring

• after successive generations the whole bacterial population will carry the resistant DNA.

• plasmids can be transferred to other bacterial populations via horizontal gene transfer.

What are the 5 stages of Natural Selection?

1. Inherited Variation; there is genetic variation within a population which can be inherited.

2. Competition; there is a struggle for survival/environmental changes cause organisms to fight for survival.

3. Selection; environmental pressures lead to a differential reproduction within a population.

4. Adaptation; individuals with advantageous traits are more likely to survive and reproduce, passing this trait to their offspring.

5. Evolution; over time there is a change in allele frequency within the population gene pool. The advantageous characteristic will become the most common in the population and the population has adapted to its environment via natural selection.

What did Charles Darwin discover about reproduction in organisms?

Organisms overproduce offspring so there are always more offspring than can be supported by the environment. Always competition.

Define Speciation

an evolutionary process that results in the formation of a new species from a pre-existing species. It occurs when reproductive isolating mechanisms prevent two breeding organisms from producing fertile, viable offspring

Outline how speciation occurs?

1. If two populations face a geographical barrier, they will experience different ecological conditions.

2. Overtime the two populations will adapt to different environmental conditions and gradually diverge from one another.

3. Variation within a species allows for speciation to occur as gene pools of the 2 populations change overtime.

4. eventually the 2 populations will diverge into separate species and be unable to interbreed to produce fertile offspring.

What four things make up the Binomial Classification system of nomenclature?

1. Genus

2. species

3. Underline

4. Universal system, agreed on by taxonomists.

What are the three DOMAINS of life?

1. Eukarya - eukaryotic organisms

2. Archaea - prokaryotes in extreme conditions

3. Eubacteria - prokaryotes in common pathogenic forms

Define Taxonomy

the science involved with classifying groups of organisms on the basis of shared characteristics

How do you classify Eubacteria?

Kingdom

Phylum

Class

Order

Genus

Family

Species

What is the difference between Artificial Classification and Natural Classification?

1. Artificial classification; randomly selecting unifying characteristics and then grouping organisms accordingly

• easy

• stable (does not change)

• does not show evolutionary relationships

2. Natural Classification;

• grouping organisms based on similarities and then identifying shared characteristics

• all members of a group have a shared common ancestor

• classifications change when new information is discovered.

How many phyla in the Kingdom Plantae?

12

Features of Bryophyta and examples:

• no leaves, roots or stems

• spores

• no xylem/phloem, no vascularisation

• mosses, liverworts, horn roots

Features of Filicinophyta and examples:

1. has leaves, roots and stems

2. uses spores

3. has phloem and xylem

4. ferns like bracken

Features of Coniferophyta and examples

1. has vascularisation

2. has leaves, roots and stems

3. reproduce via seeds in cones

4. pine trees and conifers

Features of Angiospermophyta and examples

1. has vascularisation

2. has leaves, roots and stems

3. reproduces by seeds in ovules

4. all flowering plants and grasses

Features of Porifera and examples

• asymmetrical

• no mouth or anus

• silica or CaCO3 based spicules

• sea sponge, venus flower basket

Features of Cnidaria and examples

• radial symmetry

• mouth

• no anus

• tentacles

• jelly fish, sea anemones, coral

Features of Platyhelminthes and examples

• bilateral symmetry

• mouth

• no anus

• flattened body shape

• tape worms and planaria

Features of Annelida and examples

1. bilateral symmetry

2. mouth and anus

3. body has ringed, specialised segments

4. earthworms and leeches

Features of Mollusca and examples

1. bilateral symmetry

2. mouth and anus

3. visceral mass

4. may have a shell

5. snails, slugs, octopi, squid

Features of Arthropoda and examples

• bilateral symmetry

• separate mouth and anus

• jointed body sections

• hard exoskeleton

• insects, crustaceans, crabs, spiders, scorpions, centipedes

Features of Chordata and examples

• bilateral symmetry

• separate mouth and anus

• dorsal nerve tube

• mammals, birds, reptiles, amphibians, fish