1) The document discusses how sperm have evolved traits that drive speciation and the evolution of new species. Sperm are small, motile, and genetically diverse due to meiosis, putting selection pressure on diploid cells.
2) Experiments on fruit flies showed that sexual selection and male mating behaviors were important determinants of reproductive influence, not sperm size or number.
3) Studies suggest population size can be used to trace evolutionary traits related to sexual selection, though genetic drift must be ruled out as the sole cause of any evolutionary processes observed.
Overview
In simpler terms, Evolutionary Genetics is the study to understand how genetic
variation leads to evolutionary change.
Evolutionary Genetics attempts to account for evolution in terms of changes in gene
and genotype frequencies within populations and the processes that convert the
variation with populations into more or less permanent variation between species.
The central challenge of Evolutionary Genetics is to describe how the evolutionary
forces shape the patterns of biodiversity.
Evolutionary Genetics majorly deals with;
a. Evolution of genome structure
b. The genetic basis of speciation and adaptation
c. Genetic change in response to selection within populations
Overview
In simpler terms, Evolutionary Genetics is the study to understand how genetic
variation leads to evolutionary change.
Evolutionary Genetics attempts to account for evolution in terms of changes in gene
and genotype frequencies within populations and the processes that convert the
variation with populations into more or less permanent variation between species.
The central challenge of Evolutionary Genetics is to describe how the evolutionary
forces shape the patterns of biodiversity.
Evolutionary Genetics majorly deals with;
a. Evolution of genome structure
b. The genetic basis of speciation and adaptation
c. Genetic change in response to selection within populations
An informative, rather enjoyable presentation & explanation of Neo-Darwinism (evolution) based on the theory in my 12th-grade book.
Remember: When assigned a group project, always give proper and equal time to each member. (Designed for teamwork)
An informative, rather enjoyable presentation & explanation of Neo-Darwinism (evolution) based on the theory in my 12th-grade book.
Remember: When assigned a group project, always give proper and equal time to each member. (Designed for teamwork)
NOKIA Case - Vorstellungspräsentation für Advico Young & RubicamOliver Scherrer
Zur Einleitung des Vorstellungsgespräches für die Stelle als Praktikant in der Strategischen Planung bei Advico Young & Rubicam erstellte Oliver Scherrer eine kurze Vorstellungspräsentation für die mögliche Weiterentwicklung der Marke NOKIA.
Sollten Sie an der gesamten Präsentation interessiert sein, kontaktieren Sie mich via Mail oder Telefon. Gerne präsentiere ich Ihnen meine Idee bei einem persönlichen Gespräch
7 THE CELLULAR BASISOF INHERITANCEFigure 7.1 Each of u.docxalinainglis
7 | THE CELLULAR BASIS
OF INHERITANCE
Figure 7.1 Each of us, like these other large multicellular organisms, begins life as a fertilized egg. After trillions of cell
divisions, each of us develops into a complex, multicellular organism. (credit a: modification of work by Frank Wouters;
credit b: modification of work by Ken Cole, USGS; credit c: modification of work by Martin Pettitt)
Chapter Outline
7.1: Sexual Reproduction
7.2: Meiosis
7.3: Errors in Meiosis
Introduction
The ability to reproduce in kind is a basic characteristic of all living things. In kind means that the offspring of any organism
closely resembles its parent or parents. Hippopotamuses give birth to hippopotamus calves; Monterey pine trees produce
seeds from which Monterey pine seedlings emerge; and adult flamingos lay eggs that hatch into flamingo chicks. In kind
does not generally mean exactly the same. While many single-celled organisms and a few multicellular organisms can
produce genetically identical clones of themselves through mitotic cell division, many single-celled organisms and most
multicellular organisms reproduce regularly using another method.
Sexual reproduction is the production by parents of haploid cells and the fusion of a haploid cell from each parent to form
a single, unique diploid cell. In multicellular organisms, the new diploid cell will then undergo mitotic cell divisions to
develop into an adult organism. A type of cell division called meiosis leads to the haploid cells that are part of the sexual
reproductive cycle. Sexual reproduction, specifically meiosis and fertilization, introduces variation into offspring that may
account for the evolutionary success of sexual reproduction. The vast majority of eukaryotic organisms can or must employ
some form of meiosis and fertilization to reproduce.
7.1 | Sexual Reproduction
By the end of this section, you will be able to:
• Explain that variation among offspring is a potential evolutionary advantage resulting from sexual reproduction
• Describe the three different life-cycle strategies among sexual multicellular organisms and their commonalities
Sexual reproduction was an early evolutionary innovation after the appearance of eukaryotic cells. The fact that most
eukaryotes reproduce sexually is evidence of its evolutionary success. In many animals, it is the only mode of reproduction.
Chapter 7 | The Cellular Basis of Inheritance 153
And yet, scientists recognize some real disadvantages to sexual reproduction. On the surface, offspring that are genetically
identical to the parent may appear to be more advantageous. If the parent organism is successfully occupying a habitat,
offspring with the same traits would be similarly successful. There is also the obvious benefit to an organism that can
produce offspring by asexual budding, fragmentation, or asexual eggs. These methods of reproduction do not require
another organism of the opposite sex. There is no need to expend energy finding or a.
1. The Sperm Responsible For Driving
Selective Speciation
Biology with Psychology C1C8
Jananan Nandakumar
090137918
2. Jananan Nandakumar (090137918)
Biology with Psychology C1C8
New Scientist Article 1
Dr Rhonda R Snook Wednesday 18th
January 12pm
The Sperm Responsible For Driving Selective
Speciation
The idea on how species diverged through
a process initially termed ‘transmutation of
species’ was presented by Jean Baptiste
Lamarck in 1809 and later re-debated,
visualised and comprehensively proven by
Charles Darwin in 1895, in which he
argued in favour of natural selection as the
predominant factor of speciation.
Darwin believed species formed when
animals became isolated in their
environment, so specific traits become
formed within a group or subgroup of
species. This was partly as a result of
survival of the fittest occurring, in which
the stronger species adapted and bred,
leading to their ultimate survival in the
changed environment over others. His idea
that this process of natural selection occurs
over time in which organisms were able to
evolve separately, from a common
ancestors, develop various unique traits
that would help to promote their unique
traits over others , living in the specific
habitats or environments, was published in
a book title “On the Origin of Species”
received an overwhelming attention.
This being said we can say that all species
are inter-related by an evolutionary tree
where a single ancestor promoted the
evolution into different forms of life over
time. The result is speciation, and is
defined as the process in which an original
species diversifies and splits into new
species. For this to occur we need two
species that are heading in different
directions and have no common genetic
mutation or sequence that allows them to
stem and evolve into a specific direction.
For this form of selection and speciation to
occur, all species will be required to
reproduce via the process of fertilization
and formation of a zygote; that is sperm
fertilising an egg. Sperms have many
desirable traits making them a prime
evolutionary vehicle to promote sexual
reproduction (Figure 1). The abilities of
sperm range from being motile and small
to being able to be different in genetic
makeup (genetic variation) as a result of
meiotic divisions and recombination thus
putting a selection pressure (stress) and/or
advantage on the diploid cells for either a
successfully fusion with an egg or
selective survival of the offspring over
their progeny.
Figure 1: Sperm in rodents having selectively
evolved a hook to ensure better attachment to
the egg (Snook et al, 2009)
3. However, not all organisms possess such
gametes and do not require such means
(e.g. with algae). Added to this, some
organisms have more than two mating
types, such as the organism found on algae
called stylonchia. So why is there an
overwhelming preference to gamete
dimorphism in which the sperm is a
predominant reproductive factor? Surely, it
was selection that resulted in the sperm
evolving from an isogamy state (first
ancestral state). However, different models
present interesting theories as to which
may be the fundamental cause for the
selection of the sperm.
The isogamy model predicts that the
morphology of gametes was the same at
one point in time. The pseudoanisogamy
model on the other hand predicted that
gamete size varied resulting only in similar
sized gametes fusing with other similar
size gametes. This conjured up the
understanding of evolutionary model
called the anisogamy theory in which
gametes of different sizes and classes were
able to mate. Finally evolution has
processed a system in which gamete
dimorphism being so large, lead to the
production of small and motile gametes
becoming the perfect reproductive tool.
Interestingly though, as evolution has
occurred, the size and mass of the egg has
become greater than that of the sperm by
some 1000 fold in certain examples of
species. This can only occur if certain
selective pressures are placed on
individuals, leading to a prominent
direction in evolution taking place. For this
evolution of sperm and egg to occur the
frequency must also greatly intensify. In
order for this mono-directional selection to
have occurred the gametes must i) present
strong motility (so the time taken to find
their fusion partner is quicker), and ii) the
amount of gamete productivity must
increase (to give a greater chance of
fusion).
This was often scrutinised by a previous
misunderstood theory which interpreted
gamete size as a function of fitness, which
is, obviously, not the case seen. These we
can see are the common traits present in
sperm; which must have evolved over time
in a mono-directional means to produce
effective reproduction. The knowledge on
how sexual patterns are selected is still
questionable, evolutionary scientists such
as Dr Snook and her colleagues have come
up with means to test this particular type
of selection.
To test these hypotheses, Dr Snook used
drosophilia pseudoobscura, a type of fruit
fly species with several desirable
characteristics, to perform their
experiments. One important feature of this
fruit fly is that it is a heteromorphic
species, where both sterile and unsterile
sperm are produced. Results from Dr
Snook work on these heterotrophic fruit
fly proved that sexual conflicts along with
male mating behaviour and ejaculating
traits were prime alterations for
determining mating influence. Added to
this it was noted that sexual selection was
not dependant on size or the number of
sperm (testis mass).
Interestingly though, those mosquitos that
presented large accessory glands presented
greater mating opportunities. Other studies
have shown that population size is varied
and not dependent on genetic diversity.
Primarily these investigations have
highlighted the use of population size as
means of tracing evolutionary traits that
can be specific for sexual selection.
However, with these studies on the sexual
selection, the results can only be relevant if
genetic drift does not cause such an
evolutionary process, and if results were
only due to this sexual selection. To avoid
this it has been suggested to carry out
microsatellite surveys where additional
information of selection pressures can be
4. carried out to promote the reasoning
behind a selection choice.
These findings, help us understand a
greater motive behind the selection and
specification of species, and could argue in
favour of Darwin’s idea of the fittest
surviving. The idea of the sperm being
selectively driven down an evolutionary
path parallel to that of trait selection
pressures could also be a fundamental
point to drive not only selection but
evolution within species. This being said,
it is still important to closely analyse fully
the traits that have driven species to
selectively characterise and choose a mate,
therefore developing the promotion,
evolution and speciation and survival.
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