This document discusses isolating mechanisms and theories of speciation. It defines isolating mechanisms as any factors that prevent interbreeding between related groups. There are two main types of mechanisms: pre-mating (preventing mating) and post-mating (preventing hybrid formation). Theories of speciation include gradualism, where new species evolve slowly over long periods, and punctuated equilibrium, where species remain largely unchanged apart from brief periods of rapid change leading to speciation. The key differences between these theories are that gradualism involves continuous small changes while punctuated equilibrium involves long periods of stasis punctuated by sudden speciation events.
This document will help you and will clear your concepts about the terms of Orthogenesis, Allometry & Adaptive Radiations, which are usually studied in evolution.
This document will help you and will clear your concepts about the terms of Orthogenesis, Allometry & Adaptive Radiations, which are usually studied in evolution.
Speciation is the evolutionary process by which reproductively isolated biological populations evolve to become distinct species.There are few mechanisms through which this process can be well understood.
The process by which a new species develops from the existing species is known as speciation.
Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book On the Origin of Species. He also identified sexual selection as a likely mechanism, but found it problematic.
A species can be defined as one or more populations of interbreeding organisms that are reproductively isolated in nature from all other organisms.
When populations no longer interbreed, they are thought to be separate species.
There are four geographic modes of speciation in nature, based on the extent to which speciating populations are isolated from one another: allopatric, peripatric, Parapatric, and sympatric.
Speciation may also be induced artificially, through animal husbandry, agriculture, or laboratory experiments.
Allopatric speciation: It is regarded as the most common type of speciation. It involves the physical separation of a species into two groups. This may occur due to climatic changes, movement of tectonic plates leading to the fragmentation of a mass of land, or eruption of a land mass, formation of waterways, or due to the presence of an impassable mountain range.
Parapatric mode of speciation: It occurs due to partial spatial isolation of populations, and is characterized by a small overlap in their ranges as well as significant gene flow amongst the populations. However, the gene flow reduces due to changes in the local conditions, and the two populations become reproductively isolated.
Sympatric mode of speciation: It involves the formation of new species due to a genetic divergence among a few members of the species inhabiting a single geographic area. Unlike the other modes of speciation, here genetic divergence does not arise due to increase in geographic distance, but occurs within the same niche.
Peripatric speciation was Proposed by Ernst Mayr. In this type of speciation, a small group of members inhabiting a peripheral region of the range undergo reproductive isolation to form a new species. Many a time, it is considered to be a variation of allopatric speciation.
types of orientation- primary and secondary, different types of kinesis - orthokinesis and klinokinesis and taxis - tropotaxis, klinotaxis, menotaxis, transverse orientation, dosal light reaction and ventral light reaction
Taxonomic Collections, Preservation and Curating of InsectsKamlesh Patel
Taxonomy: Taxonomy is the science of defining and naming groups of biological organisms on the basis of shared characteristics.
The classification of organisms is according to hierarchal system or in taxonomic ranks (eg; domain, kingdom, phylum class, order, family, genus and species) based on phylogenetic relationship established by genetic analysis.
Taxonomic Collection : Biological collection are typically preserved plant or animals specimens along with specimen documentations such as labels and notations.
Dry Collection - Dry collections consist of those specimens that are preserved in a dry state.
Wet Collection - Wet collections are specimens kept in a liquid preservative to prevent their deterioration.
Speciation is the evolutionary process by which reproductively isolated biological populations evolve to become distinct species.There are few mechanisms through which this process can be well understood.
The process by which a new species develops from the existing species is known as speciation.
Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book On the Origin of Species. He also identified sexual selection as a likely mechanism, but found it problematic.
A species can be defined as one or more populations of interbreeding organisms that are reproductively isolated in nature from all other organisms.
When populations no longer interbreed, they are thought to be separate species.
There are four geographic modes of speciation in nature, based on the extent to which speciating populations are isolated from one another: allopatric, peripatric, Parapatric, and sympatric.
Speciation may also be induced artificially, through animal husbandry, agriculture, or laboratory experiments.
Allopatric speciation: It is regarded as the most common type of speciation. It involves the physical separation of a species into two groups. This may occur due to climatic changes, movement of tectonic plates leading to the fragmentation of a mass of land, or eruption of a land mass, formation of waterways, or due to the presence of an impassable mountain range.
Parapatric mode of speciation: It occurs due to partial spatial isolation of populations, and is characterized by a small overlap in their ranges as well as significant gene flow amongst the populations. However, the gene flow reduces due to changes in the local conditions, and the two populations become reproductively isolated.
Sympatric mode of speciation: It involves the formation of new species due to a genetic divergence among a few members of the species inhabiting a single geographic area. Unlike the other modes of speciation, here genetic divergence does not arise due to increase in geographic distance, but occurs within the same niche.
Peripatric speciation was Proposed by Ernst Mayr. In this type of speciation, a small group of members inhabiting a peripheral region of the range undergo reproductive isolation to form a new species. Many a time, it is considered to be a variation of allopatric speciation.
types of orientation- primary and secondary, different types of kinesis - orthokinesis and klinokinesis and taxis - tropotaxis, klinotaxis, menotaxis, transverse orientation, dosal light reaction and ventral light reaction
Taxonomic Collections, Preservation and Curating of InsectsKamlesh Patel
Taxonomy: Taxonomy is the science of defining and naming groups of biological organisms on the basis of shared characteristics.
The classification of organisms is according to hierarchal system or in taxonomic ranks (eg; domain, kingdom, phylum class, order, family, genus and species) based on phylogenetic relationship established by genetic analysis.
Taxonomic Collection : Biological collection are typically preserved plant or animals specimens along with specimen documentations such as labels and notations.
Dry Collection - Dry collections consist of those specimens that are preserved in a dry state.
Wet Collection - Wet collections are specimens kept in a liquid preservative to prevent their deterioration.
Species are groups of actually or potentially interbreeding populations which are reproductively isolated from other such groups. The biological species concept has been prevalent in the evolutionary literature for the last several decades and is emphasized in many college-level biology courses. It is probably the species concept most familiar to biologists in diverse fields, such as conservation biology, forestry, fisheries, and wildlife management. Species defined by the biological species concept have also been championed as units of conservation. The species concept for most phycologists is based on the morphological characters and hence the term ‘species’ means morphospecies. On the other hand, for evolutionary biologists, the term means biological species that can be defined as a reproductive community of populations (reproductively isolated from others) that occupy a specific niche in Nature.
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Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
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Bills have a main role in point of sale procedure. It will help to track sales, handling payments and giving receipts to customers. Bill splitting also has an important role in POS. For example, If some friends come together for dinner and if they want to divide the bill then it is possible by POS bill splitting. This slide will show how to split bills in odoo 17 POS.
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2. ISOLATING MECHANISM
Definition:
Any factor which prevents the interbreeding between even the related groups of living
organism is called isolating mechanism.
The phenomenon of inability of living organism to interbreed is called reproductive
isolation.
According to Meyer(1942), reproductive isolating mechanisms are the biological
properties of individuals which prevent the interbreeding of naturally sympatric
populations.
3. When interbreeding between subgroups of a populations, called Demes, progressively decreases
and gives progressively less fertile hybrids, the various sub groups(demes) eventually become
different species.
Deme
A
Deme
B
Deme
C
Deme
B
Deme
D
Deme
A
Deme
C
Deme
D
Splitting of a population by a barrier
4.
5. TYPES OF ISOLATING MECHANISM
I. Pre-mating mechanism:
These prevent the copulation and fusion of gametes of interspecific crosses by:
a. Geographic isolation:
In this, organisms are separated by geographical barriers such as water bodies,
mountains, deserts etc. which prevent interbreeding between them.
So processes like natural selection occurs independently on both side and leads to the
formation of new species.
Example: Darwin’s finches on Galapagos island.
6.
7. b. Spatial isolation:
In this, individuals isolated by long distance are unable to breed due to their inability to
cover long distance.
8. c. Seasonal or temporal isolation:
The breeding season of the animal of one species is different from that of other species,
so are reproductively isolated.
Example: American toad (Bufo americana) breeds in early part of rainy season, while
Fowler’s toad(B. fowleri) breeds in later part of rainy season, so are reproductively
isolated.
9.
10. d. Ecological or habitat isolation:
Mating inability between the organism of closely related species or sub species
occupied the same region but different habitat.
Example: Two species of Rana that is Rana grylio(pig frog),and R. areolata(Gopher
frog) live in different habitat. So the two species show ecological isolation.
11.
12. e. Ethological isolation:
Different mating behavior of two species prevents interbreeding.
Example:
Males of different species of Sticklebacks have different mode of nest building and
courtship dancing behavior.
13.
14. f. Physiological isolation:
Mating inability due to functional incompatibility in their mating.
Example: swelling of vaginal mucous membrane of Drosophila in case of interspecific
mating.
15. g. Mechanical isolation:
This type of isolation occur due to the difference in morphological structure such as
external genitalia.
Example:
Snails of same species have reproductive structure that align but snails from different
species part other species.
16.
17. II. Post- mating mechanism:
If the efficient pre- mating mechanism fails then post- mating prevent the hybrid
formation.
These are of five types:
a. Gametic mortality:
In case of external fertilization, the sperm may fail to fertile the egg due to
unfavorable climate conditions, in case of internal fertilization, the sperm of different
species may be immobilized or killed in female genital tract.
Example
Sea cucumbers release their sperm and eggs into open water. The sperm recognize
their own species through chemical marker.
20. c. Hybrid inviability:
In this, hybrid zygotes fail to develop as the embryo formed by interspecific crosses
abort during development.
Example:
Hybrid between the Rana pipens and R. sylvatica do not survive beyond the early
gastrula stage
21.
22. d. Hybrid sterility:
In most of the organism hybrids are sterile due to incompatibility of chromosomes.
Example:
Mule produced by crosses between male ass and mare.
23.
24. e. Hybrid breakdown:
In certain case hybrids are fertile but progeny is weak, abnormal or sterile. In other
cases first generation hybrids are viable and fertile or future generations are inviable
or sterile.
Example:
Hybrids of lions and tigers have been obtained through zoo breeding programs while
the first generation may be healthy, hybrid become weak and sterile in future
generation.
25.
26. Significance:
1. It maintains the distinctiveness of characters in different species.
2. It helps in accumulation of variation leading to speciation.
3. It divides a population into sub-populations, which will differ significantly from
ancestral population, helps in speciation.
27. SPECIATION IN TIME
Speciation occurs when gene pool of a population is somehow reproductively isolated
from other population of the parent species and no longer gene flow occurs between
them.
On the basis of period taken in speciation there are two types of mechanisms of
speciation.
28. GRADUALISM
The concept of gradualism is given by James Hutton and Charles Lyell.
Gradualism states that each new species evolves gradually over long span of time. The
principle idea is that the large phenotypic differences that produced the emergence of
new species are due to the slow accumulation of many small genetic changes.
29.
30. SOME BASIS CHARACTERS OF
GRADUALISM
• Evolutionary change happens over a long period of time.
• Change happens in slow, gradual changes.
• Change is consistent over time.
• Changes are not noticeable over a short period of time.
31. Examples of gradualism:
Certain moth in one population gradually adopt change in color and wing shape
after a great deal of time, the two groups of moths develop in to entirely distinct
species from one another.
32. Over a long period of time tigers develop the combination of orange and black stripes
so they are better able to hide in tall grasses.
33. Ancestry of horse:
• Gradual increase in height.
• Reduction in the number of functional digit.
• Increase in the size of crown of molars for chewing and grazing grass.
34.
35. PUNCTUATED EQUILIBRIUM
Punctuated equilibrium is proposed by Niles Eldredge and Stephen Joy Gould.
They suggest that “during punctuated equilibrium, a species exist essentially
unchanged for long periods of time, during which it is in equilibrium with its
environment.
Theses equilibrium periods are punctuated by short period of evolutionary change,
during which its features may change rapidly.
36.
37. SOME BASIC CHARACTERS OF
PUNCTUATED EQUILIBRIUM
The phenomenon of punctuated equilibrium is often supported by the fossil records.
Most speciation is cladogenesis rather than anagenesis.
38. Example:
A species of worms lives in the soil in a particular climate and is in a state of stasis.
Climate change cause the ph. of soil to change. The change in ph. causes some
worms to die. But those that survive adopt and reproduce with new ability to
withstand the ph. change in soil the species returns to stasis.
Ancestry of giant panda.
39.
40. COMPARISON BETWEEN GRADUALISM AND
PUNCTUATED EQUILIBRIUM
Gradualism Punctuated equilibrium
I. Speciation occurs gradually. I. Speciation occurs rapidly and then a
species remain unchanged.
II. Fossils will show changes over time. II. Fossils showing intermediate
characteristics will not necessarily be
found.
III. Ancestral species can be transformed into
a new species.
III. A sub population of the ancestral species
become a new species.
