Diversity of organisms

Question 1

What is an organism?

Answer 1

An organism is an individual plant, animal, bacterium or any other living thing.

Question 2

How immense is the variety of organisms today?

Answer 2

The variety of organisms alive today is immense.

Question 3

Example supporting that the variety of organisms today is immense

Answer 3

Consider the differences between humans, trees growing taller than 100 meters, fungi that consist of a network threads growing through the soil and brightly coloured bacteria inhabiting volcanic pools at temperature above 80°C and pHs below 2. Even chimpanzees, who are animals which we are closely related to are different from us in many ways.

Question 4

Is there less variation among the members of a single species?

Answer 4

There is less variation among the members of a single species, but there are still differences between all individuals.

Question 5

When is there least variation?

Answer 5

There is least variation when 2 individuals are genetically identical.

Question 6

Example of when there is least variation

Answer 6

In humans, monozygotic twins are formed when a zygote or early stage embryo divides and develops into 2 individuals. Such twins start out with the same genes but even they acquire differences through mutations and because the environment in which they develop is never identical.

Question 7

What are the advantages of the diversity of organisms?

Answer 7

The diversity of organisms adds to the richness of the natural world and helps to make biology such a fascinating subject.

Question 8

Why is variation essetial?

Answer 8

Variation is essential for the future of life because evolution by natural selection could not happen without it.

Question 9

What soon becomes obvious when studying organisms in an area?

Answer 9

If organisms in an area are studies, it soon becomes obvious that each individual is a member of a group with recognizable traits or characteristics.

Question 10

What are the names of groups of organisms based on?

Answer 10

These groups of organisms are often given a name in the local language, especially if they are used by people or have an impact in other ways.

Question 11

Example of what the names of groups of organisms are based off of

Answer 11

For example when Maoris arrived in New Zealand about 800 years ago, they found tree ferns growing in the forests and used them to build the walls of their houses. They recognized 7 different types of tree fern, which they names wheki, kuripaka, toukura, mamuka, punui, ponga and katote.

Question 12

What did biologists begin to do in the 17th century?

Answer 12

From the 17th century onwards, biologists used the term “species” for a group of organisms with shared traits. Biologists have been naming and classifying species ever since.

Question 13

Who created the theory of morphology?

Answer 13

Carl Linnaeus, who worked in the 18th century, was a pioneer of the research about species. Linnaeus and other biologists of his time described the outer form and inner structure of typical members of a species. This is known as morphology.

Question 14

What is morphology?

Answer 14

Morphology is the idea of a species as a group of organisms that share a particular outer form and inner structure is the morphological concept of a species.

Question 15

Would Linnaeus and his contemporaries have said that origins of species was the work of a creator?

Answer 15

If asked about the origins of species, Linnaeus and his contemporaries would probably have said that they were the work of a creator. They would have thought that each species was created from nothing and remained unchanged after its creation. When describing the morphology of species, early biologists believed they were looking at evidece of a creator’s work.

Question 16

What is the international system biologists use for naming species?

Answer 16

The international system biologists use for naming species is called the binomial system.

Question 17

How does the binomial system work?

Answer 17

Each species name consists of 2 words. The first name is the genus name. A genus is a group of species that have similar traits. The second name is the species or specific name.

Question 18

What are the rules that the binomial nomenclature?

Answer 18

1. The genus name begins with an uppercase (capital) letter.
2. The species name begins with a lowercase (small) letter.
3. In typed or printed text, a binomial is shown in italics.
4. After a binomial or genus name has been used once in a piece of text, it can be abbreviated to the initial letter of the genus name with the full species names (eg. Linnaea borealis turns into L.borealis)

Question 19

According to the morphological species concept what is a species?

Answer 19

According to the morphological species concept, a species is an unchanginging group of organisms with clear differences in external form and internal structure between it and other species.

Question 20

Does the morphological species concept with the concept of evolution by natural selection?

Answer 20

It does not fit with the concept of evolution by natural selection proposed by Charles Darwin in 1857.

Question 21

Is is difficult to find a concept that describes species and fits all concepts?

Answer 21

Biologists have looked for a new concept to describe species, but it has proved extremely difficult to find a definition that fits all contexts. So far, at least 30 different definition have been suggested.

Question 22

What is the meaning of species according to the biological species concept?

Answer 22

The biological species concept defines a species as a group of organisms that can successfully interbreed and produce fertile offspring.

Question 23

What does the biological species concept explain?

Answer 23

This concept explains how a group of individuals can exist as a coherent unit as the members of a species interbreed and therefore share genes in a gene pool.

Question 24

What is a limitation of the biological species concept?

Answer 24

The biological species concept works well with some groups of organisms.

Question 25

Example how the biological species concept works well with some groups of organisms and not others

Answer 25

For example, the genus Allium contains hundreds of species, including onion and garlic, but few interspecific hybrids have been reported in natural habitats and these hybrids are usually sterile. The garden variety “Globemaster” was deliberately bred by crossing Allium christophii with Allium macleanii and is sterile. Similarly, there are more than 600 species of conifer and interbreeding between these species is very unusual. Where interspecific conifer hybrids do occur, they are usually sterile. This is partly because many conifers have no close relatives, for example, Ginkgo biloba. In conifer genera where speciation is occurring rapidly, such as junipers and pines, there is some interspecific hybridization and it is less easy to identify species.

Question 26

When does the biological species concept become difficult to apply?

Answer 26

In other groups of plants and animals, the biological species concept is very difficult to apply, due to geographical separation and gradual divergence. Further difficulties arise when migration brings closely related but apparently distinct species together.

Question 27

According to the biological species concept, what does it suggest when hybridization of 2 species occurs?

Answer 27

According to the biological species concept, hybridization of 2 species suggests that those species are not different.

Question 28

Example of how hybridization can suggest that the 2 species are not different

Answer 28

For example, captive lions and tigers have sometimes hybridized producing offspring know as liger (male lion and female tiger) or tigons (male tiger and female lion). Male ligers and tigons are infertile but female hybrids are sometimes fertile. A rigorous interpretation of the biological species definition would be therefore consider lions and tiger to be the same specie,s but this is not acceptable to biologists or the wider public.

Question 29

What is a population?

Answer 29

A population is a group of organisms of the same species, living in the same area at the same time.

Question 30

What does it mean when 2 populations live in different areas?

Answer 30

If 2 populations live in different areas, they are unlikely to interbreed with each other. This does not necessarily mean that they are different species. If they are physically and genetically similar, both populations are part of the same species.

Question 31

What happens if 2 populations do not interbreed?

Answer 31

If 2 populations of a species do not interbreed, they can diverge. Recognizable physical differences may develop as the populations become genetically more different.

Question 32

What happens when differences between species continue to accumulate?

Answer 32

If differences continue to accumulate, the 2 populations may eventually become separate species. Because this process is usually very gradual, it can be difficult to decide whether 2 populations have become separate species and biologists sometimes disagree.

Question 33

What is a fundamental characteristic of any species?

Answer 33

A fundamental characteristic of any species is its chromosome number.

Question 34

What can happen to the number of chromosomes during evolution?

Answer 34

During the evolution of a species, this number can change: it can decrease if chromosomes become fused together or increase if splits occur. There are also mechanisms that can cause the chromosome number to double. However, changes to the chromosome number are rare and usually there is no change in a species over million of years.

Question 35

Why do plants and animals have an even number of chromosomes?

Answer 35

In most plants and animals, body cells have an even number of chromosomes. This is a consequence of sexual reproduction.

Question 36

Explain how a new life begin?

Answer 36

A new life starts by fusion of a male gamete and a female gamete, with each gamete containing one set of chromosome (9 in cabbage). This fusion of games produces a zygote with 2 sets of chromosomes (18 in cabbages). All cells produced form the zygote by mitosis inherit these 2 sets of chromosomes. Gametes with 1 set of chromosomes are haploid. Body cells with 2 sets are diploid.

Question 37

Is there immense diversity in chromosome numbers in plants and animals?

Answer 37

There is immense diversity in chromosomes number among plants and animals.

Question 38

What are the number of chromosomes in humans and chimpanzees?

Answer 38

Humans have 46 chromosomes and chimpanzees, who are our nearest relatives have 48 chromosomes.

Question 39

Is there a parallel with the numbers and sizes of chromosomes?

Answer 39

There is a parallel with the numbers and sizes of chromosomes in plants and animals. Some have a few large chromosomes and others have small ones. Researchers experimented by fusing the 16 chromosomes of yeast cells to reduce the chromosome number to 4 or even 2. Their findings suggested that the actual number of chromosomes in a species is not very significant, as long as all members of the species have the same number.