Ecology
Summary
TLDRIn this introductory zoology lecture, Dr. Hill delves into the fundamentals of animal ecology, explaining how organisms interact with both living and non-living elements of their environment. The lecture covers key concepts such as heterogeneity, the competitive exclusion principle, and niches, emphasizing the importance of understanding these interactions for the geographical distribution and abundance of animal populations. It also explores population characteristics, including growth rate, sex ratio, and survivorship, introducing the idea of carrying capacity and its impact on population growth. The lecture concludes with a discussion on community interactions, keystone species, and biodiversity, highlighting the intricate balance within ecosystems.
Takeaways
- πΏ **Ecology Definition**: Ecology is the study of how animals interact with both their organic and inorganic environment.
- π **Purpose of Ecology**: The main goal of ecological studies is to understand how diverse interactions influence the distribution and abundance of animal populations.
- π **Heterogeneity**: Heterogeneity refers to the availability of resources that allow different species to coexist in an environment.
- π« **Competitive Exclusion Principle**: No two species can occupy the same niche at the same time, emphasizing the uniqueness of a species' role in its environment.
- π **Niche**: A niche is the complete set of activities and conditions that a species needs to survive and reproduce in its environment.
- π **Population**: A population is a group of individuals of the same species that interbreed and live in the same area.
- π **Demography**: Demography is the study of population characteristics such as growth rate, sex ratio, and survivorship.
- π **Survivorship Curves**: Survivorship curves graphically represent the proportion of a cohort surviving over time, showing different life history strategies.
- π± **Reproductive Strategies**: Iteroparity and semelparity are two reproductive strategies; humans exhibit iteroparity, reproducing multiple times, while many animals like insects are semelparous, reproducing once then dying.
- π **Population Growth**: Population growth is determined by the difference between birth and death rates, influenced by the carrying capacity of the environment.
- π³ **Communities**: Communities consist of multiple populations that interact with each other, with relationships that can be beneficial, detrimental, or neutral.
- π **Keystone Species**: A keystone species plays a crucial role in a community, and its removal can lead to significant changes in the community structure.
- π **Biodiversity**: Biodiversity is the variety of species in an area, with higher biodiversity often resulting from competition and availability of resources.
Q & A
What is the definition of ecology according to the lecture?
-Ecology is defined as the study of how an animal interacts with its organic as well as inorganic environment, focusing on understanding how these diverse interactions influence the geographical distribution and abundance of animal populations.
Why is the term 'heterogeneity' important in ecology?
-Heterogeneity is important in ecology as it refers to the amount of resources available in an environment, which is crucial for the coexistence of different species.
What is the competitive exclusion principle in ecology?
-The competitive exclusion principle states that no two species can occupy the same niche at the same time, implying that species must differentiate in their niches to coexist.
What does the term 'niche' refer to in the context of ecology?
-A niche refers to the role an animal plays in its environment, including what it feeds on, how it reproduces, and how it interacts with similar species.
What is a 'population' in ecological terms?
-A population is a reproductive, interactive group of a single species, identified by individuals that reproduce with one another.
What is an example of an isolated population known as a 'deme'?
-An example of a deme is the brown trout located in Georgia, which is subject to different environmental conditions and may evolve differently from other demes over time.
What is 'demography' in the context of population studies?
-Demography is the study of characteristics that measure how a population's interactions take place, including growth rate, sex ratio, and survivorship.
How can survivorship be represented graphically?
-Survivorship can be represented graphically using a survivorship curve, which plots the percentage of individuals surviving against the age represented as a percent of maximum lifespan.
What are the three theoretical survivorship curves discussed in the lecture?
-The three theoretical survivorship curves are: one where most individuals die of old age, one where species take care of offspring but are subject to mortality by other means, and one where many offspring are produced but only a few survive to adulthood.
What is the difference between 'iteroparity' and 'semelparity' in terms of reproductive strategies?
-Iteroparity refers to species that can reproduce multiple times in their lifetime, while semelparity refers to species that reproduce only once and then die, which is common in many animals on Earth.
How does 'carrying capacity' affect population growth?
-Carrying capacity is the maximum population size that an environment can sustain without being degraded. Population growth can occur when the population is below the carrying capacity, but if it exceeds this capacity, the population must decrease.
What is a 'community' in ecology and how does it differ from a 'population'?
-A community in ecology is a group of populations that interact with each other. Unlike a population, which consists of a single species, a community is made up of different populations that may have various types of interactions, such as beneficial, detrimental, or neutral.
What is 'parasitism' and how does it differ from 'commensalism'?
-Parasitism is an interaction where the parasite benefits at the expense of the host. In contrast, commensalism is an interaction that benefits one population without affecting the other, although further studies often show that the neutral party may also experience some benefit or detriment.
What is 'mutualism' and why is it significant in ecological interactions?
-Mutualism is an ecological interaction where both populations benefit from the interaction. It is significant because it represents a positive relationship that can enhance the survival and success of both species involved.
What is a 'keystone species' and why is it important in a community?
-A keystone species is a population that plays a crucial role in its community, such that its removal would significantly alter the community structure. It is important because it helps maintain the balance and diversity within the community.
What is 'biodiversity' and how does competition between populations influence it?
-Biodiversity refers to the variety of species in a defined area. Competition between populations drives biodiversity up, as more resources such as habitat, food, and water allow for a greater variety of species to coexist.
Outlines
πΏ Introduction to Animal Ecology
The first paragraph introduces the topic of animal ecology, defining it as the study of how animals interact with both organic and inorganic elements of their environment. It emphasizes the importance of understanding these interactions to determine the distribution and abundance of animal populations. The concept of heterogeneity is introduced to describe the availability of resources for species coexistence. The competitive exclusion principle is also discussed, explaining that no two species can occupy the same niche simultaneously, which influences species distribution and specialization.
π Demography and Survivorship in Populations
This paragraph delves into demography, which is the study of population characteristics such as growth rate, sex ratio, and survivorship. The growth rate is tied to reproduction, while sex ratio considers the balance between males and females. Survivorship is highlighted as a critical measure of how well organisms survive, with factors like resource availability and predation affecting it. Survivorship curves are introduced, illustrating different patterns of mortality across species' lifespans, from those that die of old age to those with high offspring mortality.
π Reproductive Strategies: Iteroparity and Semelparity
The third paragraph discusses two reproductive strategies found in nature: iteroparity and semelparity. Iteroparity refers to species that can reproduce multiple times throughout their lives, which is contrasted with semelparity, where species reproduce only once before dying. The vast majority of animals are said to exhibit semelparity, with insects being a common example. Understanding these reproductive strategies is crucial for studying population dynamics and species survival.
π Population Growth and Carrying Capacity
This section examines population growth, which is determined by the difference between birth and death rates within a population. A stable population has equal rates of birth and death, while a growing population has more births than deaths, and a decreasing population has more deaths than births. The carrying capacity of an environment is introduced as the limit to population growth due to finite resources. The population growth curve is explained, showing how growth rates increase over time until they level off at the carrying capacity.
π³ Community Interactions and Keystone Species
The fourth paragraph explores the concept of communities, which consist of interacting populations. It discusses various types of interactions, including parasitism, commensalism, mutualism, and competition, each with its own implications for species survival and community structure. The importance of keystone species is highlighted, with examples such as elephants and starfish, which have a significant impact on their communities. The removal of a keystone species can lead to drastic changes in the community composition and function.
π Biodiversity and Its Importance
The final paragraph concludes the lecture by discussing biodiversity, which is the variety of species in a given area. It explains that competition between populations can drive biodiversity, and that a greater availability of resources typically leads to higher biodiversity. The paragraph uses examples of different organisms, such as amphibians, mammals, plants, and insects, to illustrate the concept of biodiversity. The importance of biodiversity for the health and resilience of ecosystems is emphasized.
Mindmap
Keywords
π‘Ecology
π‘Heterogeneity
π‘Niche
π‘Population
π‘Demography
π‘Survivorship Curve
π‘R/K Selection Theory
π‘Carrying Capacity
π‘Community
π‘Biodiversity
π‘Competitive Exclusion Principle
Highlights
Introduction to ecology and its definition as the study of how animals interact with both organic and inorganic environments.
The importance of understanding ecological interactions to determine the geographical distribution and abundance of animal populations.
The concept of heterogeneity in ecology, referring to the availability of resources for species coexistence.
The competitive exclusion principle stating that no two species can occupy the same niche at the same time.
Definition of a niche as what an animal does in its environment, including feeding, reproducing, and interactions with similar species.
Explanation of a population as a reproductive interactive group of a single species.
The concept of a deme, an isolated population of the same species with a specific gene pool.
Characteristics of a population including growth rate, sex ratio, and survivorship.
Demography as the study of population characteristics that measure interactions within a population.
Survivorship curves representing different life history strategies of species.
Differentiation between iteroparity and semelparity in reproductive strategies of species.
Population growth as the difference between birth and death rates within a population.
The carrying capacity concept and its impact on population growth and sustainability.
Communities as groups of populations that interact with each other, with various types of interactions.
Types of ecological interactions including predation, parasitism, commensalism, mutualism, and competition.
The role of keystone species in a community and their impact on the ecosystem's structure.
Biodiversity as the variety of species in a defined area and its relation to resource availability.
The conclusion of the lecture on ecology, summarizing the importance of ecological studies for understanding species interactions and environmental impacts.
Transcripts
hi students welcome to zoology i'm your
professor dr hill i'm an assistant
professor of biology at stillman college
and today we're going to go into our
first lecture entitled animal ecology so
let's get started
so the first thing we want to look at is
an introduction to ecology by defining
what ecology is
ecology is how an animal interacts with
this organic as well as its inorganic
environment
the main point of ecology studies
or ecological studies rather is to
understand how these diverse
interactions influence
the geographical
distribution
and abundance of animal populations so
as you can see
ecology is very important
because it really goes into how animals
interact with their environment whether
it is
their living
um environment
as well as the aspects of the
environment that may not necessarily be
living
um and how they're able to take in
different chemicals as well as
um resources in order to survive
in an environment that has more
heterogeneity
there are more
availability for species to coexist so
you'll want to remember that word
heterogeneity
which just goes into the amount of
resources that are available
in order to help
any species coexist together
also you'll want to know that the
competitive
exclusion exclusion principle rather
says that no two species
can occupy the same niche at the same
time
so you'll want to understand what a
niche is in order to understand the
competitive exclusion principle
um and a niche is what an animal does
in its environment so this can be
what it feeds on
how it reproduces
how it interacts with similar species
and so forth
um so that would be the niche
so you'll want to know
that since you know what an inch is now
no two species can occupy the same niche
at the same time so
there will have to be different species
at different places
um occupying different niches
um when there is a niche
um
being occupied
you'll want to understand that there
will be the same species um occupying
that niche
so next we want to look at a very
important um
component of our
study of ecology and that would be your
populations
so a population is a reproductive
interactive group of a single species so
the main thing you want to understand to
identify what a population is to
remember
um you want to remember that they're
going to reproduce with one another
um and this is going to be a single
species
so i have
an example at the bottom you see this
picture of a school of fish
and they all look exactly the same why
because they reproduce with one another
and that um
identifies them to be
an interactive group of one single
species right
um you also want to know that
an isolated population of the same
species has a specific name
and this is called ademi
an example of edemi would be
the brown trout which is located in
georgia and the brown trout
that is located in germany
members within ademi are of the same
gene pool and thus they are subject to
different environmental conditions
than other demi deeming
natural selection however may
over
generations cause differences
in appearance or eventually lead to new
species of given enough time and some
examples of that would be
the islands
bio
geography
extinction
the bottlenecks also known as the
cheetahs
so that's your population so what else
do we need to know about a population
let's look into
the population characteristics here
and so you want to understand what
uh demography is okay this is the study
of the characteristics that measure how
a population's interactions
um
are going to take place so you're going
to
consider when you're thinking about
demography is your growth rate number
one
your sex ratio
and also a very important component
known as survivorship
okay
so the growth rate would be um
you know it's based on reproduction
right how large can the population
actually get
um based on how quickly
you know
reproduction is taking place
then you have a sex ratio where you'll
be considering males versus females and
survivorship which goes into how well
um those
specific organisms are able to survive
right the health of a population can be
determined by
your demographic terms
so number one in a population that has
no juveniles in the population this
could be a sign that something is
hindering reproduction
number two you want to look at
survivorship which tells us how many
individuals from any given cohort
will likely make it to maturity okay so
like i said before how well are they
going to survive but to be specific this
goes into
are they going to make it to adulthood
or maturity
there are many factors that affect
survivorship some of them
are going to be number one a lack of
resources
another one is an increased
predation
but it could also be just a part of the
life history of the species so you know
it's not necessarily just like the
resources or
whether or not there are predators
present
um but it can just go into the history
of the species
um
you can actually calculate survivorship
on a curve
and you do this with the percent of the
percent i'm sorry of individuals who are
surviving
and you'll put that on your y-axis
and then the time on the x-axis so
survivorship is something that can be
calculated and it can be shown using a
graph
so let's take a look at that graph that
we have here
and this is known as the three
theoreticals survivorship curl curves
okay
um so what we're looking at here um
is a graph like i said on the y-axis
you see
the number of survivors okay
and then on your x-axis you see the age
represented as the percent of maximum
life span
of those species right
and then you have three different curves
so we're going to look at the first one
first
um and that first curve represents
where most individuals die of old age
this is where most people fall
okay and then we'll look at the second
curve
this curve is a species that takes care
of offspring
but is subject
to mortality
by other means than age so this could be
predation or a lack of food as we spoke
of before
and then you have your next curve which
is the third one
and this curve is a species that has
many
offsprings but only a few survive to
adulthood so some examples of this can
be found in your fish
your insects as well as your clams okay
so you'll want to
be aware of this survivorship curve and
be able to you know critically think
about it and when you think of different
populations
i want you to
identify which curve you think those
particular organisms may relate to
okay
so let's move on next and we're going to
go into a component
known as
iteral parity versus another component
known as
samuel parity so what do these words
mean
so as it turns out the human
reproduction plan of being able to
reproduce multiple times in a lifetime
is called
intro parity
um it is not the norm however
all species are not able to
reproduce multiple times
um and so they would not be considered
in a row parity right
um
the vast majority actually of animals on
earth exhibit
um
thermal parity and they are only able to
reproduce
once and then they die
um and so an example of this is seen
here um in the picture i have
um where are all the dead animals right
um
and you'll see this a lot in insects
okay and we'll talk about insects a lot
in this class so you want to remember
these two
different types of reproductive plans
for life
so let's move on to
population growth right because that's
one of those components
that's very important when it comes to
ecology um and as we talked about
survivorship right we looked at the
curve
so while survivorship deals with a
single cohort
population growth is the difference
between the rates of birth and the
population and the rates of death
in the population so essentially you're
comparing
how many people are dying
okay and how many people are being born
okay that's called population growth
so
um if you have more individuals being
born and less individuals dying then
you're going to have high population
growth
if you have more individuals dying than
are being born then that's going to be
low population growth
um
so if a population has just as many
deaths as birth that population is
considered stable
it would be at the top of the curve on
the right
if a population has more births than
deaths then the population is growing if
the population has more deaths than
births then the population is decreasing
how much a population increases or
decreases is going to depend
on the resources available so you'll
want to remember that
every environment has a finite amount of
resources available and these are called
the carrying capacity of those organisms
so when a population is below is
carrying capacity
it can grow
but if it exceeds the carrying capacity
it must decrease okay so you'll want to
understand how carrying capacity affects
the population of growth
so let's take a look
at our population growth curve here
and you'll see that on our y-axis we
have the number of individuals right
and then on the x-axis
we have time so as time goes on we
should see
a decrease or a decline
in our population growth so the curve
here shows
that
the growth rate is increasing over time
and any any and it
increases i'm sorry it increases
um until it gets to the carrying
capacity right
so you'll see here at the bottom the
growth rate increasing and then
eventually it gets to where the growth
rate starts to decrease once it reaches
the carrying capacity so that's how
carrying capacity affects your growth
curve
so now we're going to move on to another
type of organization level
known as your communities okay so we
talked about population so let's look at
how a
community is a little bit different than
a population
so a community
is groups of populations which are going
to be interacting with each other okay
so remember that
so communities are actually made up of
populations
but they're different populations right
they interact with each other
so they have interactions between those
populations
that can be detrimental okay so if
they're detrimental then they'll be
represented by
a minus sign
they can also have interactions that are
beneficial so if it's beneficial it'll
be represented by a plus sign
on the other hand they can also have
populations i'm sorry not populations
but interactions
that are neutral
and if they're neutral they'll be
represented by a zero
okay
so the interaction between a predator
and a prey
for example is considered beneficial for
the predator
which is a plus sign
but it's detrimental for the prey right
so that would be a minus sign right
the next component as it pertains to
interactions um in our community is
known as
parasitism all right
parasitism also has the plus or the
negative interaction
where the parasite
is going to benefit and the host is
going to
not be able to benefit okay
um so it's going to be
decremented
so the next type of interaction we want
to look at is known as commensalism
commensalism is an interaction that
benefits one population with the plus
sign
but it also has no effect on the other
so commensalism is a good sign
because there's a benefit but then it's
neutral
um
for the other
organism
so there have been many proposed
examples
of this however
further study into the interaction shows
the neutral party has a benefit
um or a detriment okay so you'll see an
example here at the bottom of an
elephant
zebras
giraffe
um so those are different populations
right
but they actually
have formed a community right because
they have to interact with each other
and there's an accident and there's an
excellent example of the elephant here
who's providing a benefit to the zebras
by
spraying them with water for example
right you see the elephant spraying the
water on the zebras
so they do get some type of a benefit
from being in a community with the
elephant however you don't see
a predator which could be considered a
lion
and you probably know that lions eat
zebras
um
and so they
are going to create um
a non-beneficial
um interaction for our zebras for
example okay
so that's just an example so let's move
on and we're going to look a little bit
more into our communities
and we want to look at an interaction
known as mutualism okay
what is mutualism this is both this is
when you have both populations that are
getting some type of a benefit
from the interaction so that would be a
plus plus
and then
you also have competition
okay and competition is going to be a
negative negative because
um this is by far the most common and
probably the most important interaction
in nature
because in an environment that has
finite amount of resources populations
will have to compete for those resources
or risk becoming extinct
okay so in a community each population
will have their niche which we talked
about they'll have that thing that
they're doing
and the competitive exclusion principle
tells us that no two populations can
share the same niche
but most species niches will overlap
to a degree
where resources are shared
okay so when niches overlap species
become specialized by
partitioning the resources okay so
there's an example here
of um
how there can be a partitioning of
resources in
what is called your
cichlids
and also your wood wobblers
alright so that's just an example
of partitioning the resources
next we want to move on to a concept
known as a keystone species this is
found in your communities
sometimes a population
is so important in a community
that if it's removed from a community
the entire community will change okay
and if the population is this important
that particular organism is known as a
keystone species okay
so i have two examples here um the first
example is obvious because i have a
picture of it that's your elephant um
elephants are known as keystone species
because they play a very important role
in their
community in that they're able to
provide
um
a lot they they do things like
um
they they're able to travel through
thick areas of forest and woods
um
and knock down
um
that
you know forest
or those shrubs and trees and bushes to
create pathways
and those pathways actually allow other
organisms to be able to
um travel
to resources okay and it also helps um
humans as well because they create
roadways and that's just one that i can
think of off the top of my head um that
you probably didn't know
because they're so big they are able to
create
um
like roadways
and transportation access
to resources because they're able to
push down trees and bushes
um they also are able to
you know use their trunks to
break down trees and
those trees can be used for different
things and you know the community as
well
so if they're taken away from their
environment you can imagine
you know that's going to cause a lot of
problems so elephants are very important
another example in
um
you know the water
is going to be your starfish
in an aquatic environment
um starfish are able to play a very
important role as well okay so those are
your examples of your keystone species
next we want to go into biodiversity so
what is biodiversity
this is the same amount of species in a
defined area
on average rates of
speciation are going to exceed rates of
extinction
in earth's history if this wasn't the
case then
animals would not be able to in their
own species survive
it has been shown that competition
between populations actually drives
biodiversity up
the more resources
such as the habitat the food the water
etc
the more
biodiversity a commercial a community
can have okay so when you think about
biodiversity think about this picture
is many different organisms
that are going to
um play their role
in order to
um
you know be a part of
biodiversity so you have a well
an aquatic environment a frog for
example on earth
frogs are
um
able to live in water as well as on land
they're amphibians because of that
and then you have a monkey and then you
have a flower which is a plant as well
as a bee
okay so that's an example of bio
diversity
all right so that concludes our lecture
on ecology
um hopefully you learned a lot um i hope
that you're able to study this material
um and i look forward to seeing you
again
on our links our next i'm sorry our next
lecture
thanks
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