A3.1 Diversity of Organisms

Biological Species Concept

a group of organisms that can breed and produce fertile offspring

Population meaning

Group of organisms of same species living in the same area at the same time.

Speciation

process by which new and distinct species arise from a single ancestral lineage

Two populations diverge

recognizable physical differences may occur

population become more genetically different

differences accumulate and the two pops eventually become separate species

Diversity of chromosome numbers of plant and animal species

• chromosome number of a species is a fundamental characteristic

• the number can change during evolution

• these changes are rare and take place over millions of years

• we have 46 and chimpanzees have 48

• diploid number of chromosomes is evenKa

Karyograms

A karyogram is an image showing the karyotype of an organism (chromosomes of an organism in homologous pairs in decreasing length - the characteristic types of chromosomes in a species)

Classifies chromosomes by length, band pattern and centromere position

Genome

all the genetic info of one individual organism or group of organisms

Gene

functional length of DNA carrying a sequence of hundreds of bases

Homologous

same genes in the same sequence along the chromosome

Alleles

alternative forms of a gene - differ in base sequence

Single - nucleotide polymorphisms (SNPs)

Positions in a gene where more than one base may be present

Most bases are the same in all humans

SNPs are the main factor that makes humans different from one another

Genomes of eukaryotes can vary in size and base sequence

• variation in genome size

  • measured in base pairs

  • large genomes contain large amounts of junk DNA (transposons)

• variation of base sequences

  • two pops of a species will have differences in base sequences

  • if pops diverge, more differences accumulate

  • some vital genes barely ever change

  • distantly related individuals are likely to have identical genes for these vital functions

Dichotomous key

use for identification of a species within a group

Biological species concept issues

Asexually reproducing species

• only 1 parent, don’t interbreed to produce offspring

• produces offspring that are usually genetically identical

Horizontal Gene Transfer

when the transfer of genetic material is between organisms rather than from parent to offspring

different to vertical transfer, which is genetically passed from parent to offspring

HGT is particularly common in prokaryotes, including bacteria