Ecology

Summary

In 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

• 🌿 **Ecology Definition**: Ecology is the study of how animals interact with both their organic and inorganic environment.
• 🔍 **Purpose of Ecology**: The main goal of ecological studies is to understand how diverse interactions influence the distribution and abundance of animal populations.
• 🌐 **Heterogeneity**: Heterogeneity refers to the availability of resources that allow different species to coexist in an environment.
• 🚫 **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.
• 🏠 **Niche**: A niche is the complete set of activities and conditions that a species needs to survive and reproduce in its environment.
• 🐟 **Population**: A population is a group of individuals of the same species that interbreed and live in the same area.
• 🔑 **Demography**: Demography is the study of population characteristics such as growth rate, sex ratio, and survivorship.
• 📊 **Survivorship Curves**: Survivorship curves graphically represent the proportion of a cohort surviving over time, showing different life history strategies.
• 🌱 **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.
• 📈 **Population Growth**: Population growth is determined by the difference between birth and death rates, influenced by the carrying capacity of the environment.
• 🌳 **Communities**: Communities consist of multiple populations that interact with each other, with relationships that can be beneficial, detrimental, or neutral.
• 🔑 **Keystone Species**: A keystone species plays a crucial role in a community, and its removal can lead to significant changes in the community structure.
• 🌈 **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

00:00

🌿 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.

05:03

📊 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.

10:03

🐛 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.

15:04

📈 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.

20:04

🌳 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.

🌐 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.

Keywords

💡Ecology

Ecology is defined as the study of how animals interact with their organic and inorganic environment. It is central to the video's theme as it sets the stage for understanding the various interactions and dependencies within ecosystems. The script uses ecology as a foundation to explore topics like animal populations, niches, and environmental factors influencing survival.

💡Heterogeneity

Heterogeneity refers to the variety and distribution of resources within an environment. In the script, it is mentioned as a factor that influences the coexistence of species, as a higher level of heterogeneity allows for more resources and thus the potential for a greater diversity of species to coexist.

💡Niche

A niche is described as the role an animal plays in its environment, including what it feeds on, how it reproduces, and how it interacts with similar species. The concept is crucial for understanding the competitive exclusion principle, which states that no two species can occupy the same niche at the same time, as it explains species distribution and specialization.

💡Population

A population is defined as a reproductive interactive group of a single species. The script emphasizes that populations are essential for studying ecology because they represent groups of organisms that interact and reproduce with one another, which is vital for the survival and evolution of species.

💡Demography

Demography is the study of population characteristics, focusing on factors like growth rate, sex ratio, and survivorship. In the video, demography is used to understand how populations change over time and how various factors can affect the health and sustainability of a population.

💡Survivorship Curve

The survivorship curve is a graphical representation showing the proportion of a population surviving to different ages. The script introduces three theoretical survivorship curves to illustrate how different species may experience varying rates of survival and mortality throughout their lifespan.

💡R/K Selection Theory

R/K Selection Theory is referenced through the terms 'iteroparity' and 'semelparity'. Iteroparity refers to species that can reproduce multiple times in their lifetime, while semelparity refers to those that reproduce only once and then die. This theory is important for understanding the different reproductive strategies of species and how they adapt to their environments.

💡Carrying Capacity

Carrying capacity is the maximum population size that an environment can sustain indefinitely. The script explains that population growth is influenced by the carrying capacity, as it represents the limit to population growth due to finite resources. Understanding carrying capacity is essential for managing and conserving species populations.

💡Community

A community is a group of populations interacting with each other. The script discusses how communities are composed of different populations that have various types of interactions, which can be beneficial, detrimental, or neutral. Understanding communities is key to grasping the complex web of relationships within ecosystems.

💡Biodiversity

Biodiversity refers to the variety of species within a defined area. The script highlights that biodiversity is driven by competition between populations and the availability of resources. It is illustrated with examples of different organisms playing their roles in an ecosystem, emphasizing the importance of biodiversity for ecological health and stability.

💡Competitive Exclusion Principle

The competitive exclusion principle states that no two species can occupy the same niche at the same time. This concept is used in the script to explain how species must differentiate and specialize to coexist in the same environment, leading to the partitioning of resources and the avoidance of direct competition.

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